It should be mentioned that the Timeskip designs, for the Straw Hats at least, vary significantly by arc. Like they're straight up different costumes between the major post-timeskip arcs. Distinguishing between Wano costume Nami (post #7480920), Fisherman Island costume Nami (post #7493059), and so on, is still going to be a matter of appending something else to the search (i.e. the costume's qualities e.g. Bikini for Fishman Island).
For characters like Nami, Luffy, Zoro, Robin and Sanji the post-timeskip tag would mostly just be distinguishing their generally taller and sexier appearances. Though it is very helpful for Franky and Chopper since their design changes are much more drastic.
Perhaps should be pointed out: the way the FE3H timeskip tags were done, only the post-timeskip designs got a tag. Pre-timeskip FE3H characters just use the normal character tag and that's it. Though I suppose that may have been because nearly every pre-timeskip FE3H character wears like the same costume.
But still on an individual character basis, each Straw Hat really only has one unique costume design during the pre-timeskip, so I question if the pre-timeskip character tags are needed and we can just use the defaults for their (one) pre-timeskip costume.