Unlike what another answer suggests, I think that "continuum hypothesis" is not a good tag to use as a proxy here. 

Instead, I assume many of these questions would be about "cardinal characteristics", so maybe we need such a tag. It seems to me that "cardinal characteristics" would be more useful than the proposed "small uncountable cardinals", which seems to me to be a bit vague in scope. I also don't see what the advantage of using it be. For instance, many results involving forcing axioms are about the combinatorics at $\aleph_1$ and $\aleph_2$. I don't see any gain in having this tag added to questions about such results. 

I understand that "cardinal characteristics" may be specific enough that a few questions that would use the "vague" tag may be left out, but it seems like a useful compromise.