What do you mean with "disassociate the mtext"?
Do you want only the mtext to remain from selected mleaders?
If so, try this:
The OP is referring to Qleader and
NOT Multileader, and they want to
delink the connection between Mtext and Leader objects so the text won't follow the leader if leader object moved / relocated after all and that what it's called disassociate.