Z control isn’t strongly supported in EZCAD2 based devices - and the vast majority of galvos do not have Z control abilities (in software) as a result.
With a small dev team, we must focus on the features that affect the largest number of users. Z control simply isn’t the top of the list at this time.
With that out of the way, I hope this honest reply satisfies. We do have a Feature Request page (hyperlinked) that already has this suggested - you can vote for it here: Live Z Axis on galvo laser · LightBurn