Drop-proof your pack
Girth hitch a 60 cm sling to your pack when you’re on a multi pitch.
If it has a solid clip point and the pack isn't too heavy, you can use that. If you wanna be sure nothing's going to break, you can put it through your shoulder strap.
Keep a spare carabiner on the sling. (Here I have a locker; non-locker is probably gonna be fine too.)
When you reach the belay, clip the pack to the anchor, and THEN take the pack off. Doing this makes it pretty much impossible to drop your pack.
