Removal of the "scripts\" folder causes a issue with the "Monitor File Changes" setting in the Script Editor. It prevents the Script Editor from seeing file changes done in external editors.
While deleting some files and folders from my test install folder I accidentally included the "scripts\" folder. mIRC was closed at the time of the deletion and the folder only had default scripts and files included in a new install.
I tested on a copy with mirc.exe and mirc.ini in the same folder. Also tested on a copy of mirc.exe installed elsewhere while using %appdata%\Roaming\mIRC\ for the mirc.ini and "scripts\" folder. I got the same issue.
1, Verify this setting is enabled/checked: Tools -> Script Editor -> Options -> Monitor File Changes
2, Load/Create a script in a different folder like C:\temp\foobar.mrc.
3, Exit mIRC.
4, Delete "scripts\" folder.
5, Start mIRC.
6, Edit foobar.mrc in external editor like notepad.
7, Save file in external editor.
8, *BUG* No "mIRC File Changed" dialog.
If you recreate the "scripts\" folder after modifying the script in a external editor the "mIRC File Changed" dialog will appear in a few seconds or so.
I used v7.72 non-beta release in this testing.