> I'd personally prefer to see a single, customizable integer for
> multiples, instead of selecting 5 and 10 arbitrarily.

A single, customizable integer does not solve my use case, which is to highlight tens and fives differently.

It'd be possible to add two faces, line-number-Nth-line and line-number-Mth-line, and add variables to customize that N and M instead of what I've done.

But, are you suggesting it just because it is more generic, or do you have an use case for another integer?