Minimizing minecraft 1.12.2 with cmd block menu open causes the game to not let you press Done. only cancel.
()() Reproducing this issue ()()
(1) Use /give <name> command_block
(2) Place it and right click as always.
(3) Minimize the screen.
- A little bit more detail, but when I put to full screen it lets you press done after you put a command in the block.