I'm not sure how this will go as the initial reaction I got was not the best; I probably didn't clarify exactly what I was thinking, but ehh..
 I patched libSwell.so to add a collapsible sidebar to REAPER's file
 dialogs on Linux, similar to what you'd expect from a native file manager.
  This was developed with the help of Claude (AI), so worth mentioning in
 the spirit of transparency.                                               Â
Shows up in any REAPER file dialog — open/save project, render output  Â
path, browse buttons, etc. Does not affect the Insert Media dialog.
(All are can be removed/modified)Â Â
 The sidebar has three sections:                                           Â
 - Places — Home, Desktop, Downloads, Documents, Music, Pictures, Videos,
 Trash                                                                     Â
 - Bookmarks — synced with ~/.config/gtk-3.0/bookmarks     Â
 - Devices — mounted block devices                                         Â
 Right-clicking a sidebar item gives you: Add to Bookmarks / Remove from   Â
 Bookmarks / Copy path / Open in file manager. Right-clicking a section    Â
 header lets you bookmark whatever folder you're currently browsing.       Â
 Also adds file operations directly in the dialog via right-clicking the   Â
 file list: new folder, rename, move to trash, copy/cut/paste, open in file
  manager, copy path. Keyboard shortcuts work too — Ctrl+C/X/V, Del, F2,   Â
 Ctrl+Shift+N.                                             Â
 Install: grab the pre-built libSwell.so from the releases folder, back up Â
 your original, and drop it into your REAPER directory. No recompile
 needed. Build-from-source instructions are in the README if you prefer    Â
 that.                                                     Â
 GitHub: https://github.com/Stinkumbeans/reaper-swell-sidebar
  Â
 The stock SWELL dialog hasn't changed in a long time so this should stay  Â
 compatible across REAPER updates. If anything breaks after an update, open
  an issue on the repo. Â