Yeah, no need to log the compressions, just "Removed, clean and gapped plugs, reinstalled." Since the compression test is NOT maintenance that information is not required to be entered.
What I would do is just track the compressions in a separate 'unofficial' document.
That's what I would do too, and it sounds like others here would as well.
I think this thread really got derailed when the insistence was to write the values in the logbook. I don't understand the obsession with this, if the numbers need to be written down they can be documented in a separate notebook.