Hello Blenderheads, got the 4.3 version and realize my (quite big) brush library is not compatible with the new system, any workaround? would prefer not remaking all the brushes by hand 
Currently, the process of registering as an asset is required.
Importing VDM Brushes to 4.3 - Support / Modeling - Blender Artists Community
The blender 2.79 brush is also registered.
The brush setting has not changed, but the way you manage the brush has changed.
Watch the video only where you need it.
Texture Brushes from 4.2 and previous will not show up in the 4.3 versions and above as the data structure changed when converting to assets. All of my texture paint brushes require me to recreate them in 4.3, and there is no scripting possible to make the changes unfortunately.
Strange, if I append my ten brushes from 4.2 into the current 4.3 file, they appear nowhere as they are not assets. How do you get them to show up, and where are you defining them as assets?
The registration method is the same as the sculpture brush.
Made and tested in blender 4.2 and there is no problem with registration.
If you open the file, find it in the brush list, and register it as an asset, you can check the registration right away.
You can check the registered brush in the asset management window.
If you do not see the registration brush, shut down the blender and try again.
I can get the brush to show there in the outliner as a brush, set it as asset, and then in All Libraries see the brush. Thanks for that, that is an improvement.
Problem then is that the brush says it finds no asset at the user library I have set as my path to find my brushes, so I will need to do this in the user library file first. Wonky, but saves me a lot of time of recreating brushes.
The method of bringing the brush to the scene does not work.
At the moment, this seems to be the only way. 
I’m glad you explained it though, that saved my efforts.
After appending brushes, you just have to save the file to be able to see them, in asset shelf as current file assets.
I have to save them to the file used for my other brush assets named in my preferences, right?
The newly created brush is automatically saved as an asset.
library\Saved\Brushes
However, if you register the brush you created, it will not be saved automatically.
Simply insert a newly registered brush file into the library\Saved\Brushes path to maintain the registered brush.
It seems that it can be managed in the same way as existing assets.
I think you just need to put the file in the desired location and set the path to the asset.
You can open an essentials_brushes-context.blend, append old brushes, put them in catalog of file, save the file. They will be present as essentials assets.
Or you can append your old brushes, save them in a new file and use this new file as a custom assets user library.
Or you can save each appended brush as its own brush_asset.blend file in default user library.
Or you can append your old brushes, save them in startup.blend file. So, their tweaking will be saved in all your future files, like in 4.2.
The change between 4.2 and 4.3 is just that startup.blend file has no brush.
The ones present are from asset libraries. But you can add brushes to startup.blend file, and have a similar workflow as in 4.2.
It’s still a little fuzzy for me here, since no it doesn’t allow me to open the file in 4.3 and mark them as asset - only way is to mark them as oo_1942 indicated before, but then that new file needs to be saved to where the main library is - or they again will not show up. Assets are a great idea, but this appending and marking in outliner only is for the birds if marking as asset doesn’t automatically save in the user directory.
But it’s probably me and my learning curve issues.
Put a file with a brush registered as a library into the path that is created when you create a new brush. This method is definitely possible.
But I haven’t checked if it’s possible to do it the same way as the existing library. 
Flagging th brushes as Assets does the trick for me! thank you very much!
That is up to user to define location of used asset libraries in File Paths tab of Preferences window.
Then, in Source List of asset browser or Catalog Selector of asset shelf, user can choose to show all libraries, or just essentials, or current file assets, or a user library.
That being said. Saving of brush assets is overcomplicated.
It was initially proposing same amount of choices, but was restrained to user libraries, before 4.3 release.
Developers promised an operator to duplicate them to file in development task.
But Duplicate Asset operator is unable to save a brush asset as an essential brush or in current file.
For newly created brushes, that means that user is forced to save brush in user library, and then append it in another file to be saved as an essential or a current file asset.
Developers acted as if all users would only want to save one file per brush in user libraries.
I’m not going to lie, I’m still confused now but I’ll figure it out when I can sit at the computer for a bit.
All my searches for handling this problem turned up this thread. I banged my head up and down the posts here for quite a while for the phrasing to make sense, and I eventually got it working, I’ll post a somewhat more verbose explanation. This includes an aside about a new technical wrinkle and solution as I started this task in Blender 5.0.1, trying to import old brush packs.
Thanks!
- Opening an old pre-4.3 brush pack blender file, the brushes are in the Scene Outliner > Blender Files. There one can select or multi-select the desired brushes and right click, then Mark as Asset.
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I tried Mark as Asset this in Blender 5.0.1, and they did not move correctly into the tray, loading without their thumbnails. I did not rigorously test to see what other aspects also failed. Versions 3.0.1 through 4.2.17 LTS did not allow brushes to be marked as assets. 4.3, 4.5.6 LTS both allowed marking brushes as assets and they worked as expected.
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3.0.1 was my OS’s app store/ repository version, 5.0.1 being current can be from a specific supplemental ppa, a specific deb package, a flatpack, or a snap (perhaps particular to Ubuntu and derivatives like Pop!_OS). Multiple snap versions is not supported presently so I first removed the current snap version in in the terminal,
sudo snap remove blender
- and then I used the code offered by snapcraft.io/blender with the specific version number selected to install that version.
- Following the successful Mark as Asset and the brushes moving to the asset tray, the file is saved(as) again. From here there are a few ways to utilize the marked assets in another blender file.
- Application Menu > Edit > Preferences > File Paths
- Note the file path of the User library and any further library directories you made here and want to use.
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In your file browser place a copy of this new saved-asset-brush-containing .blend file in Assets folder, at the same tier as the Saved folder you would generate when you make a brush from scratch and save a file. When you load a new blender file with that asset library those asset brushes will be available for use.
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Alternately, in the Asset Tray at the bottom of the viewport when in the relevant Drawing or Texture Painting or Sculpting modes, each asset can be individually right-clicked, in the popup menu choose to then Save Asset or Duplicate Asset (depending on the blender version) which will then create the filename.asset.blender file in the user asset library.
A) This .asset.blender file can be attached to a different open blender file by choosing File > Append
B) This .asset.blender file can be dropped into the relevant asset library folder under Assets > Saved > Brushes
Thanks again!