How would you go about changing the seven_things_plus variable via the GUI?

You can't. You can get around the filtering by other means, but that doesn't make seven_things_plus any less hardcoded.

Maybe the term hardcoded have some particular negative connotations for you. In that case please explain what that connotation may be.

The correct definition just means data in the code rather than loaded at runtime. It is not necessarily a bad thing (things like unit conversion factors are perfectly reasonable to hardcode). In this case, I'll let everyone judge for themselves if hardcoding 'enoughmuskspam' is acceptable.