allow multiple active sidebars

[ztNFny]

The new split sidebar with multiple categories makes common operations like switching between maps and adding operations quite click-heavy as one has to switch between the sidebars first to react those options.
Would be nice if instead of showing only the 1 sidebar clicking the selector would toggle the sidebar. The css already supports multiple active sidebars, it's just the toggle that needs to change.
(Also the content would have to be optimized a bit more to save on vertical space)

Screenshot of the current version, just a few "active" classes added to selectors and panels - and in red parts that could be removed (in multi-panel mode?) to save vertical space:

if you don't like it as default - maybe as a config option?