Well, Final Cut Pro works pretty much like iMovie in dealing with segments that are recorded at too low a level. The big issue is that the maximum increase in volume is 12dB which really isn't enough. The problem is that I was messing around with an OBS Studio volume filter and I recorded some too low. The issue seems to be that Zoom provides low input to OBS Studio and even at a maximum 12db gain there and 12db gain in Final Cut, the levels are too low.
And then I have the problem that my direct input is too high. Sigh. The solution is to press the "R" key in the timeline window. This is the select Range and then you can drag across the audio timeline and create an envelope and then drag in the middle to raise the level. Also, I accidentally deleted the volume on the right which you add with Windows > Workspace
But this isn't that much of a solution since Zoom is just too low on output, so I need to figure out how to increase the volume there. I'm wondering now if I can just add two Gain filters into an Audio input on OBS or use the compressor to push the volume up. So I'm going to try that next.