This question is about the tag gm.general-mathematics. A meta question about it already occurred here, but was less specific (and didn't generate much discussion). See also the discussion in the comments of this answer to the question "tags which encourage off-topic questions".
As a top-level tag, it is one of the of the arXiv math subjects. As an arXiv subject has a quite bad reputation, as it plays there some kind of trash role, e.g. to redirect unlikely proofs of fancy conjectures.
At MO I don't see the point to use it as a trash-tag, since we already have tag-removed to retag randomly tagged highly off-topic questions. And for questions that are correctly tagged but off-topic, keeping the tag is essentially harmless or even helpful (e.g., I don't see the point to remove "gr.group-theory" to a question of beginner level in group theory, even keeping it can accelerate closure).
Back to my point, my suggestion would be to use the tag gm.general-mathematics to questions where it literally applies, that is, whose field is not specific to any subfield of mathematics, but still includes some mathematical discussion (e.g., would apply to "what is your favorite trick...?" or "examples of misleading widely use notation", rather than to "Should I tell my adviser that I don't like my subject" or "Why does arXiv reject papers such that (...)"). Thus would not be just a clone of soft-question. And I would find it quite useful in such a role, even if it will naturally have a ratio of off-topic questions higher than average.
What do you think?