Hi this is not looking good. My UV editor doesn't have blue colour format and I have a very strange shape in the middle not converting and a rogue vertex. Hmm... Can I alter rogue vertex within UV editor? Quick fix?
For the blue stretch colors, click the downarrow next to the two circle icon and then in the dropdown turn on "Display Stretch"
So that's where they moved it! I've been wondering where such a useful thing went. Thanks!
The rogue vertex may be from that vert not being merged/selected when you unwrapped it. The more opaque section looks like you may have overlapping faces in that area, so maybe you duplicated a lot of faces on top of each other by accident. Try selecting all verts (A) and Merge By Distance to see if that solves the problem.
You can definitely select just that vert and move it. Standard selection and movement controls in the viewport works in the UV editor.