Very impressive! It works pretty well for me. The F2 functionality is good --- and goes way beyond the "quick notes" rubric! I see files named untitled.md, untitled~1.md etc. appearing in the current working directory --- that is probably unintended. In the XyWrite version, the entries in a directory are sorted with the subdirectories at the top, with prominent indicators that they are subdirectories, and the same key (C)subdirectories at the top and labels them clearly.) That means that, by invoking my directory-switching program and then the directory manager, from wherever I am I can open the file c:\xy\m\computer\laravel\laravel.txt with the key sequence Alt-s, U, Alt-F1, l, C, l, C, which I finded to type several more keystrokes to reach the file. Also, the subdirectories are mixed in with the files, and are not distinguished visually from them, and a different key is required to call a file and change to a subdirectory. In the directory listing, would it be better to omit the string representing the current working directory (as in the XyWrite Directory Manager)? Well, I can play around with the code and see what I can do with it!
You chose to implement the functionality in a script, which I can see has the advantage that the user can adjust it to their taste. (It is very impressive that QN already has a scripting language powerful enough to do that.) art of DIR, which would seem to have the advantage that you wouldn't have to worry about the stray untitled.md files and could perhaps implement some of the functionality in the XyWrite version of the script more easily.