Alternative bar numbers trouble

I have a piece with an alternative ending, in the form of a Coda. The ‘first’ ending starts at bar 9. I want the Coda to have 9a, 10a, 11a… (i.e. alternative bar 9.)

The ‘actual’ bar number for the Coda is bar 15. I can set the bar to start at 9 again, easy enough. If I use the Subordinate bar numbering, I get 14a (for bar 15), 14b for 16, 14c for 17, etc. I’d settle for 9a, 9b, 9c.

Can this be done?

Also, how do I show a bar number on a particular bar?
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I believe you can show a bar number by invoking a bar number change but not actually changing it… then it’ll show.

Ah: it’s not showing on my Coda in the score, for some reason.