I'd like the ability to have an option to sub chords.

An example:

Suppose you have eight bars, and at the end of the eight there are two turnaround bars, that sometimes you might go this way, perhaps chromatic, the next time you might want a 1 6 2 5.

You don't really want two verses, it is just a whim on your part, for practice, or for comparison purposes.
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Imagine grabbing the two bars in question and right clicking on 'substitute'. A Substitute window pops up with options to substitute.

You see the current chords as 'option one' there are three more boxes labelled 2-4. In these boxes are suggested subs, that can be overwritten by the user. Next to the box you desire to currently use, you can place a tick to load a turnaround.

This might need a cap at four bars, but I see it also being useful for one bar.

At parts of the song where subs are available, there would be an indicator on the main GUI chord.

Win 11 64, Asus Rog Strix z390 mobo, 64 gig RAM, 8700k