How could every bar be selected, excluding every 5th bar? I only know how to select from bar __ to bar __ (Select > Select bars) but not how to make a custom selection. Is it possible for this type of function?
You can make a "pick 'n mix" selection of objects - individual notes, text items etc. with Ctrl-click (or the Mac equivalent). But a passage selection must be a contiguous passage. So I'm afraid what you want isn't possible.