Maybe I’m not using collections correctly, but I miss having separate layers to model objects on. In previous versions, when my scene was crowded with lots of objects, it was simple and easy to just go to an empty layer and model something, and then copy it and move the copy to my main scene layer. If I needed to adjust, etc. I could just delete the copy and go back to the other layer and make some tweaks. But this “collection” idea is very convoluted to me. I want a separate area to model things in, but they invariably become part of the same collection. Seems like a lot of extra work for no perceptible advantage. If anyone knows of a good video tutorial about collections, please let me know.
I think the collections went too far 
Outliner (Header) > switch Display Mode to View Layers
Create/Add couple of Collections (as many as you need), then work with those as you’re used with Layers or Groups (M shortcut is still functional). Also check the new visibility functions (you can easily solo out)…
UI changed and with it “workflow”. But don’t worry, it’s mostly simplified. Just take some time to workout, exercise a bit to get the hang of it - you’ll soon be running around faster 
2 Likes
I like the idea of collections, Its still got some room for improvement I think. I never figured out layers. What I really don’t like is the lack of children being categorized in a dropdown under their parents…
2 Likes
They’ll also be a lot more interesting when we get the dynamic overrides system that will let you override any property/attribute at the collection level (among others).
Maybe I need more practice, and also wait for the final release.
I will try the “M” option, too. The only way I could move something from one collection to another was to copy and paste, which was not very intuitive. Took some effort to find out how to paste.
Collections can be a liability if you don’t keep them organized from the beginning of a project, or when porting a large 2.79 project over. When everything is in the proper collection, you can hide what you don’t want to see, then you have your blank space. The old layer system made no sense at all to me, coming from 2D programs like Photoshop. Say you open a file you haven’t touched in a long time, how do you know what is on each layer? You may have had some logic when you made it, but it’s very difficult (to me) to pass that logic forward because the layers are not easy to label.
Collection instancing is pretty cool within a file, and using collections to append meshes into another file is super easy too, so long as they are labeled correctly. Copying and pasting mesh into a collection won’t really help you, as you’ll have two copies, which creates more issues. Just use M to transfer a selected object to the collection you want, or to create a new one.