Instead of editing packages, just override the output directory in project options/additions and overrides (stored in the IDE) and use the FPCVER macro (or any other macro) there. You can then set these project options as default.
Nicely found. I see you can add your own IDE Macros there as well, and change their values according to your different build modes.
I agree, that UI is pretty non-intuitive. But now I've had a quick play, it certainly reproduces some of the functionality that I can deduce from the D2007 screenshot. Only thing missing from there is environment variables...