I do not understand why this should not be possible with chords. A chord is a combination of 2 key presses within a short time. The time can be configured in the key mapping configuration dialog.
I tested pressing
Ctrl+' followed by pressing key
A and it worked fine. Also pressing
Ctrl+Shift+~ followed by pressing key
N worked. Of course the standard multi-key delay is just 500 ms and therefore the keys must be pressed fast. To be honest, I have not defined
Ctrl+' and
Ctrl+Shift+~ because I'm using German keyboard which requires pressing
Shift+# to get character
' and therefore the first key sequence for this chord was
Ctrl+Shift+#. I must press on German keyboard
AltGr++ to get character
~ inserted and therefore the first key sequence for
Ctrl+Shift+~ was on my computer
Alt+Ctrl+Shift++. On a German keyboard I can insert character
á just by pressing key
´ followed by key
a.
And I made this test not with scripts. Scripts are not good in this case because too slow for simply inserting a single character. Much better is to do these character inserts by macro and collect all those macros for inserting special characters into a macro file which is set to be automatically loaded on startup of UltraEdit. All macros should have not enabled the 2 macro properties. With macros you could also make the insert of the special characters very easily file extension depended, see for example my post
German umlaut problems after converting utf-8 -> ascii.