I'm having the same issue with the TAB since moving from Sketchup 2024 to 2026.
I have used Fredoscale Box Stretching for almost 10 years as a essential part of my workflow, using TAB to insert geometry dimensions all the time.
I'm not able to find on what other toolbars or windows it focusses when pressing TAB, but what i found out that if i press SHIFT - TAB, i don't need to press TAB multiple times.
Hope this helps whoever finds this helpfull.