Well, I stopped using Rehearsal Marks for this, since they are a pain to configure and I’m generally not in favor of workarounds.
Text items should just properly avoid collisions.
What method did you use to shift it so far to the left? Dorico is not expecting system text to be placed like a rehearsal mark, so is not accounting for the bar number, obviously.
There is nothing to add here and I hope the team hears your plea.
That, alas is the main problem!