Q++ Defaults is not an allowed Language
This message occurs when editing the Languages property, if you try to select Q++ Defaults as one of the languages used in your Script. This is not allowed.
The reasons why you may have tried to select this language are :
|•||Simple mistake (too much coffee).|
|•||You have a Script in which none of the GridTemplates use any language (rare, but possible) and you want to select anything just to get rid of the design-time message No Languages are selected.|
|•||You may mistakenly think that you need to include Q++ Defaults as a language to have your tokens access it.|
In the second case, you should create a "blank" language as an immediate child of Q++ Defaults, and use that blank language for such cases. If this occurs often enough for you, you may want to use this language in your Preferences (see International Preferences). Note that since all tokens are assumed to have an "a" LanguageTag by default, even if they do not explicitely have one, there is no such thing as a GridTemplate which uses no languages.
In the third case, you should re-read the sections on The difference between a Token not being translated, and having an empty translation, and The Languages Hierarchy.