System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: TITAN V/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 456.71

Blender Version
Broken: version: 2.90.1, branch: master, commit date: 2020-09-23 06:43, hash: rB3e85bb34d0d7

Short description of error
When adding a new value or editing some values, in the keymap settings. The entire tree setup collapses after every change of any value. Not just the tree you are in, but all trees. (I have not tried other areas.)

Exact steps for others to reproduce the error
Enter the [preferences] window.
Go to the [keymap] section.
Navigate to the [3D view] area and expand that tree.

• Expand any tree-view items, then continue below...
• Expand the [3D view (Global)] area.
• - Expand the [Rotate view] area.
• - - Expand the [View 3D Rotate Modal] area.
• - - Select {+ Add New} and adjust the settings.

It is at this point that any open trees will all collapse and return to closed-state, as well as the view scrolling back to some other location from where you were. Which now requires you to scroll back to the area you were, open all the levels of the tree view again, and continue editing that new area more. (Assuming that you did not finish editing the settings. As it continues to close the tree after every change to any setting.)

Expected operation...

The tree remains open after altering or setting a value and the list does not scroll away from the area you are editing. Including any other areas you may have open, which may be open for a reference of duplicating those settings.