I can't delete markers with the delete (backspace, not forward delete) key on Mac. Maybe that key should be changeable in the controls.

it seems that the new apple keyboards dont have a button for delete... (dont mean backspace).

what i can find online is that you need to use a key combination. i would suggest trying:
shift+fn+backspace
fn+backspace
ctr+d

as for making it posible to change the keys i will add it to my todo list.