Hi in 2023,
Using the Save Editort: Gibbed.MassEffect3.SaveEdit
just change ID 21751 at bool to False if you broke up with Miranda.
Thanks to these guys right here:
https://fextralife.com/forums/t447870/how-to-save-miranda--a-complete-guide
I will change the setting back after the Quest, because I don't know what exactly it is used for :)