There are many questions about well-ordered sets on the main and I consider well-orders to be an important topic. So perhaps they could deserve their own tag.
On the other hand, many questions about well-orders are at the same time questions about ordinals so tagging them by both ordinals and (well-orderings) (or whatever the name of the new tag would be) seem to me somewhat duplicate. If we want the questions where well-orders are a relevant part of the question tagged with ordinals, making a synonym would help to achieve this. (I am not sure, which of the two should be the master tag. In any case, if we decide to use the two tags as synonymous, the tag-excerpt should mention both well-orderings and ordinals.)
To me, the best solution seems to be creating such a tag as a synonym for ordinals. EDIT: On the second thought, I am now not sure whether they should be synonyms. (But I am not totally opposed to the idea of the synonym.) I will wait and see what other users have to say about this.
Some additional comments:
- As mentioned here order-theory could possibly be used as an umbrella tag for various types of orderings, including well-orders. But this does not seems such a good idea to me. (Well-ordered sets are not explicitly mentioned in the tag-wiki for order-theory.)
- As mentioned here, we already have some questions tagged ordinals where the question does not explicitly mentions ordinals, only well-ordered sets. One such example is here.
EDIT: Since the discussion about this tag kind of ceased and received no further feedback apart from the few comments below, I went ahead and created well-orders tag. Maybe this can renew the discussion about tags for questions from this area a bit. And either we will reach the conclusion that such questions deserve a tag of their own, or a synonym (in one direction or the other) will be created.