I have this recurring editor issue where the cursor advances to the next line after entering an assignment operator (:=) or a type definition operator (::). I'm guessing the Maple code implementation is attempting some sort of code formatting and wants to advance the cursor one space beyond the operator. The only problem is that the space doesn't exist, so the cursor is ultimately advanced to the existing token in the buffer stream which in my case is a line feed; i.e., the next line.
The editor appears to be in 'Insert' mode since I can't overwrite characters while the cursor is positioned in the middle of a string. Also, toggling the Insert/Overwrite key has no apparent affect on Maple. I'll leave the issue of non-displaying(deleted) characters that appear to remain in Maple's memory buffers for another day.