If the layer UI will stay the way it is I would suggest to have the layer area (red) scroll while the options below (yellow) stay fixed.
When having dozens of layers we always need to scroll down to access layer operations.
Later when grouping is added I would also suggest that the grouping operations are located there ( yellow).
If that makes the layer area (red) too small, maybe the options area below can fade in once we stop scrolling the layer area.
To be honest though, I am not sure if the layers are in the right place to begin with.
All tabs except the layers tab are just settings and operations while the layer tab is where you can interact, reorganize, rename, select, hide etc. During modeling it is accessed constantly compared to the other tabs. i feel this window (yellow) should be separated from the options and operations.
SPACEBAR Floating Menu
The layers could be a separate window while all other tabs could be accessed with a press of the space key in a way Maya and other apps do. I have a feeling that you don’t like the idea