Pablo, we 
you!
Looks like once that patch is in, it would become a great time to make quadriflow be able to recognize these boundaries and treat them as guides.
I also wonder if it would be possible to make the voxel remesher recognize them too, would it be possible for the grid to have different densities based on user-defined regions, or even telling the remesher to not touch an area?
Things will get interesting once the rewritten multires modifier is in.
Don’t forget Zbrush’s secret smooth brush that only works on poygroups. 
Lot of people don’t know about that one.
Yep. The best part about having a polygroups system is that it opens up so many possibilities for improvements for other features across the board. It increases performance, improves remeshing quality, and more. Face Sets support for MultiRes will especially improve sculpting performance significantly like Polygroups does for SubDivs in ZBrush, which I especially am looking forward to. 
On another note, it really bothers me that the 2.83 Alpha build hasn’t updated since 4th of March. We need a new build asap!
The Windows build didn’t update today either.
Either the machine is turned off or the build script for Windows is failing. MacOS and Linux meanwhile are building fine. If the devs. don’t get it back up and running by tomorrow, then we will likely need to wait until Monday (unless someone uploads a generic build to Graphicall).
This isn’t unprecedented by any means, but some of the new stuff is looking pretty nice.
I tried the feature but unfortunately you can’t remesh by “groups” it always combines them, hopefully it’s on Pablo’s todo list because that would make multi-parts sculpting so much easier in Blender.
Definitely, although to be honest I rarely use that brush, mainly because I’m a lazy one-slider-should-do-the-job kinda guy. 
Did you also know there’s a new Smooth Mode in ZBrush (Weighted Smooth Mode # 9) that smooths only within Polygroups but leaves the polygroup borders intact?
I’ve asked about it at Devtalk:
This build on Graphicall seems to be up to date, with the face groups, but i Don’t know how to create them
https://blender.community/c/graphicall/Whbbbc/
I don’t expect that from Sculpt Face Sets.
You need to be able to handle transitions from surfaces.
OpenVDB Remesh modifier in sculpt-features branch was merging volumes and density of mesh was also uniform. You could define a different voxel size per primitive.
That does not change the fact that remeshing was uniform only respecting the smallest value.
We haven’t see such thing, anywhere. No experimental branch. No patch.
Quadriflow is there because it is supposed to handle a variability in mesh density but only a small one.
So, I don’t see a reason to expect from Blender devs a miracle for a remeshing solution before several years.
That is already great that current Remesher is preserving Sculpt Face Sets.
I find it, a little bit weird, that we have a way to created Face Sets from masked areas but not the opposite operation.
To obtain a derivative mask with a smoothed border from a Face Set, we have to hide the others, first; then, fill mask and then smooth mask.
I suppose that ability to smooth borders will make Face Sets auto-masking more useful.
But anyways, it will never be an equivalent to a mask with smoothed borders.
For Draw Face Sets brush, maybe, its UI could be purge of unnecessary settings (Sculpt Plane and Falloff, for example). But that is cool to be able to use textures.
I succeeded to have unsymmetrical results with this brush by using default Voxel Size and default Radius Unit set to View (switching it to Scene solved the problem).
We need to randomize colors very quickly. A color closed to main default Face Set often happens before having created 8 Face Sets. And we may need to repeat the operation 2 or 3 times before obtaining something satisfying.
Same random colors palette as for objects. Same issues.
I think that will help, in both cases, if a coloramp was available in Preferences and ; if a seed value was present in popover or F9 panel.
Pablo explained that in commit log.
Shift W to expand them same way that you can expand mask.
Otherwise use Draw Face Sets brush or Face Sets menu.
Press Ctrl to expand a Face Set while using brush, otherwise it creates one Face Set per stroke.
I am wandering if it would not be better to invert this behavior of brush.
have you seen this?MPC is showing some workflow of big production in Lion King.
is a bit OT,but i think it is interessting to see what Blender would need,or is missing, to play in a very big production.
Funny, not only does every Disney film have a character with a French accent, even the character creator has a French accent. 
I did indeed.
Tried Face Sets out a bit. Feels pretty nice overall. Not every keymap has been updated with the shortcuts, so it took a little bit of time to set up at first.
There are however some bugs I immediately noticed. For one, Expand Face Sets symmetry is currently broken. The side where you expand a set is always one face smaller than the opposite side, so you are then forced to use Symmetrize to regain symmetry again.
Another more serious bug is that Face Sets From Masks/Visible actually paint over to the hidden parts of your mesh, meaning that when you invert your selected set to see the hidden ones, the newly painted set will bleed over, therefore breaking your carefully selected set.
I believe @Zino.G is talking about the dynamesh “groups” feature? 
Which works like this: If you have this “groups” option enabled and your mesh has more than one polygroup, when you remesh it, dynamesh will split those polygroups into separate pieces and treat them as such. So while you have that option enabled, you can keep sculpting/remeshing and those parts won’t merge together, even though they are all still part of the same mesh.
Very useful…
Have written three bug reports now on Face Sets, two of which Pablo has already added revisions for:
https://developer.blender.org/T74498
https://developer.blender.org/T74499
https://developer.blender.org/T74501