you can have Z cycle through three modes:
- nothing. don’t show the block
- block selection (up/down) & rotation (left/right)
- block movement and placement
there is also the classical “X to select block/confirm placement, Z to cancel/pick up block”. you can swap X/Z.
also, put the block selector (the horizontal slot machine thing) outside the playable area. it makes looking at the level a bit clearer.