It would be great if paths were relative to project files in .geany files. Even the base_path. It would be helpful when working with the same project on different machines/OS.
Manually modifying the .geany files to specify relative paths works well, it even has the advantage to desplay short paths for folders.
In the same idea, specifying relative path with / instead of \\ on windows could help the cross-OS usage of projects.
(I'm using Geany v0.18 on both Windows and Ubuntu)
This feature would be great :)