Cutting to the specific example described in your post - you have a case where the date and location changed during the creation of a print (as opposed to a tour blank where somebody took a sharpie and wrote a date and venue on there by hand).
For this example, I would consider it a new piece of art and not a variant, so yes, "Adding Similar Art" is the right way to go. If you look up "EMEK Dave Matthews Band" or "Dylan Gans" in the search boxes, you'll see several examples of posters where the same image is recycled, but the date and venues are different. These are all unique posters made at different times for different audiences, and therefore unique entries.
Now, to the statement of
djve wrote:It's not clear that the "Add Similar Art" can be used to add variants.
...it can, but to be honest, it's annoying. The approver has to create a new edition, download the image to their computer, upload the image to the existing art entry, assign it to the new edition, then reject the art submittal.
Adding a variant as a new image eliminates some of those steps. We just ask that you put things like edition quantities, prices, release dates, etc in the notes section so they can be added when the new drop-down box is created.