Hi....welcome to the Club
I know exactly what you mean, when I had surgery some time ago, I couldn't have the belt tightening against me so I bought one of these clips and it worked superbly.
It doesn't hinder the seatbelt operation or cause damage but it retains it slightly off the body and doesn't retract beyond the point you attach it to on the belt.
https://www.ebay.co.uk/itm/383592771501?epid=10034692864&hash=item594fe92fad:g:mHIAAOSwElte6QPz