Should be able to delete elements with "system" flag (tempo markings etc.) when selected as part of a range
- On a new single staff score, add a tempo marking
- Select the whole measure
- Hit backspace/del (or use Edit|Delete command)
- Nothing happens
In fact as long as your selection is a range, elements with the "system" flag (meaning, extract to all parts) do not seem to get deleted at all.
There might be some circumstances this makes sense but I can't say I can think of any offhand (and you should be able to deselect using the selection filter - currently tempo markings come under "other text" that includes Staff Text. So perhaps an enhancement to the selection filter seems called for here too).