There are currently tags for simplicial-complexes and cw-complexes. The former has about 85 questions at the moment. A search for "delta complex" gives about 90 results, and there are often[weasel words] questions in algebraic-topology which discuss $\Delta$-complexes.
I have no experience with Meta and definitely none with tag creation, but I just thought that this might be a reasonable question to ask/tag to suggest, and I hope that that's the case (please let me know if not!).