Tab beams adjustment not working

"I noticed I can adjust the standard beams, but not the TAB barlines."

I think you mean the TAB beams, not the TAB bar lines. Tablature beaming can be modified with usual palette commands for beaming and 'un-beaming', but their positions cannot be changed. This is by design, to allow at least 32th notes without conflicting with tablatures strings and frets.

At the moment, there is no plan to add custom beam adjusting, but better optimization of the available space can be added in the future (for instance, by reducing the length of stems when only notes with fewer beam levels are used, as in your score). But only to a degree: if you see the last populated measure of your score, you may notice that crochet stems cannot be shortened very much.

Given your specific score, I would try lowering a bit the chord names and/or increasing a bit the distance between systems to avoid the clash between chord names and the staff above.

Thanks,

M.