We are using a third party library for that so it kind of is what it is.
We have tested the marker addition and removal with Firefox, Safari and Chrome and they all seen to work fine.
Click on the trashcan icon to select items to delete, select the items to delete, click the Save button next to the trashcan icon to save your changes.
The object you are attempting to delete should disappear when you click on it. If it isn't there is something else going on.