I've encountered the same weird glitch with my assemblies twice now since switching to SolidWorks 2020.  Sometimes, if try and edit a component within the assembly, then save & rebuild it, suddenly my workspace will be filled with what I can only describe as "dimension definitions".  They seem to act like the dimension definitions you would use in Sketches, except that they don't go away even once you exit the sketch.  Clicking on and dragging said dimensions doesn't make them go away, as even if you try and hide them within the geometry they just pop back up to their original placement as soon as you so much as breathe.  What's worse, because this glitch only occurs after I save the assembly, I can't just undo whatever action created these dimensions in the first place.  These dimensions even appear if said .sldasm file is used in other SolidWorks assemblies.  I have no idea how to get rid of these unnecessary dimensions, other than remaking the entire .sldasm file from scratch, which I'd rather try and avoid.  

Has anyone else experienced anything like this?