It works fine for both Aircrafts/Manufacturers and Models
It does NOT work for either of the Airports - Agent Names or ICAO
it works fine for Phraseology
It does NOT work for Telephony Designators.
I tried what you suggested and still cannot make a modification with a new entry. The only way I can make modifications in the Telephony Designators is by using one of the many duplicates I have. I can open a duplicate call sign and alter it to something new.
If I highlight Telephony Deignators and click on the New Modification button, it does expand the Telephony "folder" to show all the call signs, it just doesn't give me a new modification page.
** I also tried highlighting Missing Telephony Designators, but when that is highlighted, the New Modification button is not active to click.