Problems with the delete (aka rub-out) button

In the editor I am finding the delete button mysterious in operation. Usually in any kind of an editor, when you hit delete, it deletes what is at the current "cursor" position. But this one seems to have some rules that are not apparant. For instance it seems to be difficult to remove a symbol for measure beginning/ ending. Sometimes it seems like once you place one, it is there for ever. Any words of wisdom on this one ??

The delete key is mainly for Chords (and text).
For Segno (Coda etc), rehearsal letters (like IN, V, A, B etc.), bar lines etc. their buttons cycle through choices including a blank (equivalent to delete).
Try the 1st time bar indication by touching a few times.
Also you can use the UNDO button if you mistakenly have just input a symbol inadvertently.