It always vaguely bugged me when I mistyped the name of a landmark that I had to remove and re-place it, instead of just editing its name in place. Then it occurred to me that this was my code and I could do something about that.
Specifically, in v5g, when you right-click on a user-placed landmark, you now have both options "Change landmark name" and "Forget landmark". This also works from the Landmarks dialog.
And as long as we're in the neighborhood, I thought of another feature I've long wished for, and this addon seemed like the best place to put it. See, I've gotten into the habit of not opening undead pits in Dreadfell until after I've come back from the East, same as for vaults and chests there. Problem is, auto-explore keeps going back to those unopened pit doors, unlike with chests and vaults, which it will only go to once. Well, after a bit of source diving, I figured how that worked for vault doors, and now we can make it work for pit doors too: the right-click map menu for regular doors now includes a "Mark as explored" action. [NOTE: As with vault doors, I recommend you take a step or two away from the pit door after marking it and before resuming auto-explore, or it might try to open the door anyway.]