So, to anyone still looking for this function: until this gets added properly, I made this little svg as a temporary solution. It doesn't really work too well, its "clickable" surface is smaller than it should be and it doesn't scale very easily, but it's okay for a quick fix. Find the file here: (Github click the "download raw file" button on the right)
Edit: Oh, and you use it with the stamp tool, in the "User" section, then select the file with the + sign.
Edit: Oh, and you use it with the stamp tool, in the "User" section, then select the file with the + sign.