Bring back independent left/right panel collapsing (as in UI2)

One thing that’s become frustrating is that it’s no longer possible to collapse just the left panel while keeping the right panel visible.

In UI2:

• Ctrl+Shift+\ only hid the left sidebar.

• The collapse arrow on the left also only hid the left sidebar.

Now in UI3:

• Both Ctrl+\ and Ctrl+Shift+\ collapse both left and right panels.

• The collapse arrow also hides both panels together.

This makes workflows harder for users who want to maximize canvas space but still have quick access to the Inspector or Design panel on the right.

Request:
✅ Please restore the ability to independently collapse the left and right panels — both via shortcut and via the left collapse arrow.
✅ Even a setting in Preferences to toggle between “unified collapse” and “independent collapse” would be great.