Generally, when creating a new tag, there are a few key considerations (keeping in mind that a question can only have 5 tags):
- New users should be able to easily find the right tags for their question. Tag proliferation (having many highly specific tags) makes this difficult for them.
- If all of the questions that could possibly have a certain tag are already described well by another tag, then the new tag is probably not necessary. (Unless that "other tag" is extremely broad and has a huge number of questions in it.)
- Tags should help with "findability" - we try to use common words for things so that people can find tags easily. If people might search for something with a different name, instead of adding another tag for that name, we add a tag synonym which points to the other name. That way, all questions about that thing can be found under one tag.
- Tags are used for grouping questions, so in most cases a new tag should be applicable to at least a handful of existing questions.
Also, tags should describe what a question is about, not what it merely relates to. (By "what a question is about" I mean "what the OP asked us to answer" - even if you believe it's necessary to address something else in an answer, it shouldn't be used for tagging the question.) For example, we only tag a question with a country-specific tag if the question is about the conventions specific to academia in that country. We don't tag a question with united-states just because an incident described in the question took place there.
Regarding the specific proposals:
In the case of this question, the question does not ask about accommodations (whether under Section 504 or not - we don't even know if this person is in the US), so those seem to be inappropriate tags for the question. In general, any question that could be asked about 504 and accommodations is already covered by disability. This tag has only 30 questions, so it doesn't seem necessary to further subdivide it. I can see how people might search for "accommodations", so you might propose a tag synonym for "accommodations" that points to disability.
In the case of this question, the question is about what a particular exam scoring status message means, not about the OP's anxiety, so anxiety would not be an appropriate tag for the question (regardless of the appropriateness of the tag in general.) In general, we have emotional-responses which includes anxiety, discouragement, guilt, jealousy, etc. (See this meta discussion in which we came up with the name for this tag.) (This tag is for questions which specifically ask about dealing with an emotion, not questions that mention an emotion for context.) Given that there are fewer than 30 questions tagged emotional-responses, subdividing into individual emotions does not seem necessary to me. Again, you might propose tag synonyms for individual emotions if you feel it is necessary. (It would certainly help with findability.)