Feature Request - Variable Time offset

Not a huge thing but I think it would be nice to be able to set a offset on a variable time like you do with sunset or sunrise.

The use case for me would be in a rule that I use for setting up my morning heating in a bathroom. I have a start time for the routine then I base other things happening over the next couple of hours. I could setup additional variables, but it would be simpler if I could say variable time + offset minutes. That way when If I change the start time everything else just shifts with it.