I use a "portable" version of Lazarus under Windows, but I cheat :-) I map a Folder to B:\ (sometime as USB mapping, but mostly using appropriate regkey to mount a folder as B:\. I keep that folder synced across multiple PCs using Resilio Sync).
B:\ hasn't been used by Windows since the age of the floppies, so I'm never competing against other systems and my config paths don't need changing.