It would be very nice to have a menu item "Copy File Path to Clipboard" in the submenu that pops up when you right click on a file tab
Other suggestions are "Directory Path" and "Navigate to Directory" but the tree browser plugin makes up for the latter and I find the former unncessary, it's just that I'm not the only user of Geany
"Copy All Open File Paths" would be nice too, for use in batch files. I've coded both in Lua/Lua FIle System ("lfs") for another app. These are pretty simple to do.