If change custom settings in Compressor, must i reimport into FCPX?

If you save the changes in a custom setting, you will then pick it out of a list of settings when you either Send to Compressor or Share > Compressor Settings.

Russ

Let me see if I understand: say you have a custom setting in Compressor, let's call it "October", and you have a destination in FCP X, using Compressor settings, that uses this "October".

What it seems you are asking is: If you go into Compressor and modify "October" (say, change the bit rate, or frame size), is this change reflected in FCP X?

I did a little test. What I found is that you need to go into Destinations, select the destination in question, click Change... and reselect "October" from the list; otherwise the share uses the old settings.