Well the cheat engine guess may have been a good one. It seems you can edit flags using this table (https://fearlessrevolution.com/viewtopic.php?f=4&t=13996&sid=44a842e8b4f61b632361343ba1cdae6f#google_vignette), including tags like 'isDating'. I don't know if this actually works or not for getting multiple romances, and even if it does it seems like it might be a laborious headache. It's a bit beyond me, but it might be useful to someone. It doesn't work. The clear dating options don't work, still being detected by companions as in a relationship. As for the dating/romance flag itself, during my test it seems to not work either. I really hope someone can make a mod for this.