To be honest, I am surprised Geany does not have this feature already, and that no one else has requested it. I would really like to see a sidebar file browser that displays files and folders in a tree-view and lets me open files by double-clicking, like practically every IDE has.
The file browser should have an option letting me set the root folder of the browser, so that I can see only the directories I'm interested in. A feature letting me select "favorite" root folders from a drop-down list at the top of the sidebar would also be handy (like in Macromedia Dreamweaver).
Currently I'm using Anjuta for Linux development, but it's quite unstable and crashes all the time. I would like to switch to Geany but I really need a file browser to do so!