I use slots very often in my job, as I’m sure many do. I spend at least 30 minutes a day navigating the “Swap instance” UI. It would be great if I could copy the location from a nearby instance and paste it into the slot.
I think you can achieve this with my plugin Master: pick the target instance, then link the slot object to the target instance (basically copy & paste).
That said Figma doesn’t have the concept of slots natively and it’s definitely a super limiting environment using workarounds like this. Here is a suggestion you can vote for to make this a reality: Fully Editable Component Instances