To make a concrete UI suggestion, I think the file menu could be changed to:
``` New File New File (with template) >... Open Folder as Project... Open File... Open Selected File Recent Files ``` ... and the `Properties` entry expanded to a sub menu: ``` Properties > Current File Properties > Project Folder (grayed out if no project folder opened) ``` And the `Project` menu could then eventually just be removed. The new `Properties > Project Folder` would handle any settings worth keeping in a sort of `.geany-settings.yml` file in an opened-as-project folder and therefore replace `Project > Properties` in the long run.
The `Documents` tab could then be automatically opened if `Open Folder...` is done, and list the opened project folder automatically with all its files (rather than just the opened ones), or if you don't want to expand it like that, there could be a separate `Project Folder` tab that otherwise looks like the `Documents` tab but behaves that way with listing all folder files rather than just the opened tabs.