Could I possibly leave out the rum or use something other than liquor? I don’t like using liquor in my recipes. Thanks

Sharpness for rum?
Citrus? Not to my taste.
It's only a tablespoon, so I agree with Smaug...might as well just omit and not replace.
But if you want to include something else for complexity, I'd go for semi-sweet or dark chocolate; maple, date or pomegranate syrup or molasses.
All different tastes, to be sure, but picking up on the sugar base of rum.