https://ghisler.ch/board/viewtopic.php?p=444333#p444333
Usually the options menu for a window can also be opened by pressing Alt+Spase - but it does currently not work in the BTM dialog.
I looked back,and found that it stopped working in TC 1100 final - probably due to this fix:
history.txt wrote:27.07.23 Fixed: Background transfer manager: Prevent beep when pressing Alt+"+" or Alt+"-" by handling WM_SYSCHAR (32/64)