So. I am still learning the Lumetri effects and creating "looks" beyond neutralizing correcting.
I discovered that Lumetri has a vignette built in. However, even though it appears at the bottom of your effects chain, it is actually NOT. Any repositioning you do on the clip means that the vignette is also repositioned!
It also doesn't offer any edge blurring. Just darkening.
The solution I've found for now is to go back through my project and click off the vignette on each clip, then create an adjustment layer with JUST the vignette turned on in the Lumetri panel for the adjustment.
Of course, it lacks that blur. So I may throw out using Lumetri to do the vignette altogether and might mask an adjustment layer with levels and blur effects on it.
Open to other solutions.
Disappointed that the vignette feature in Lumetri is not as useful as I'd hoped.