Multiple projects open at the same time

I have not been able to find out how to do the above. One (old) suggestion was to have multiple instances of PSPad running, but the Program Settings -> System Integration menu will not allow me to uncheck "Only One Program Instance" (there is a red dot beside it). Is there another way?

Hello

If application is installed in program files, some options require to write into program folder.
Start PSpad as admin, change settings and save it. Than start PSpad normally

Many thanks.