Somewhat off topic, but related.
Ctr+-F12 gives you a list of units to open, and I assumed it was from the search paths and project paths,
Turns out that it also will look at the .dpr uses statement.
Ideally, the paths should be relative...
uses
SomeUnit in '..\RelativeFolder\SomeUnit.pas'
But, I had a stale test project in my project group where the uses path used an explicit path
uses
SomeUnit in 'c:\Obsolete.Path\to\RelativeFolder\SomeUnit.pas'
So, pressing Ctrl+F12 gave me both of these - even if Obsolete.Path didn't exist.