previous backdrop
Previous backdrop
The previous backdrop block is a stack block and a looks block that switches the backdrop to the previous one, or goes to the last backdrop if used when the stage is currently on the first listed backdrop.
Workaround
Scratch already has a "previous backdrop" option available in the switch backdrop to () and the switch backdrop to () and wait blocks, which works the same as setting the backdrop to the backdrop number - 1:
switch backdrop to (previous backdrop v) switch backdrop to ((backdrop [number v]) - (1))