There should be a way to cancel “Calculating chess move…”, make changes to the board and re-calculate the next move.
I sometimes move pieces to the wrong place, have to wait 7 seconds (until calculation complete) before I can change the board and re-calculate.
(think about those who have set think time to 15 s - they will have to wait half a minute!)
I know I can open a new tab, copy the FEN, paste the FEN, move the pieces then calculate, but that might take longer