Hello Thomas,
From your screenshot, I am guessing you are using a version of the toolkit older than 2009. The fuzzy logic tool was completely overhauled for the 2009 release and it is very simple in the new version to do what you are asking.
I tested with the older editor, and it looks like some assumptions were made that you would have a minimum of 3 linguistic terms, so I do not see a way in the editor to delete that third term. Sorry for the bad news.
I am curious to know about your application, as it is strange to have a fuzzy system where you would only have 2 linguisitic terms. As mentioned above, if you have access to the 2009 version of PID and Fuzzy Logic Toolkit, the fuzzy part of the toolkit is more robust and user friendly. The original version made some assumptions about the numbers of rules and terms and input variables you could have that limited some of the systems you could design, so if you want to design a fuzzy system, 2009 would be a better option.
Regards,
Angela M
Staff Product Support Engineer
