It’s actually quite easy to move a snapshot to a different board :
Clic on the snapshot you want to move to another board
Clic on the “move dashboard” icon that should appear to the right
Select the dashboard where you want to move your snapshot to
And voila !
For more details, check the video below :
https://www.loom.com/share/2983d5e170b34b3cae801928144b7d54?sid=9f990dac-0f97-49b2-945e-bf80798a67b9