Here is a way

The question raised by PaulaM suggests a way to do what you want:

IT Commands specify keys that IT sends to the client application (not to IT itself). So if you put {Alt+Period} in a command, this will instruct IT to send Alt+Period to the application you are currently using. You can create an entry:

 period   {command} {Alt .}_ 

Then, typing period; will send the Alt+Period directly to the application without having IT filter it.

Jean Ichbiah

PS. The trailing _ tells IT not to add a space after the expansion.