Using /thm toggle will swap to total mana view, but issuing it again will not swap back to just percentage.

Could you explain what you're doing to notice this?
I can't replicate the issue.
As a side note: It only updates it on the next mana regen update, so if toggleing while at full mana you won't notice a change. (easy fix though if that's the only issue)

You can try the attached PR branch and see if that does indeed solve what you were noticing.