Hi, welcome to the forum! Not quite sure if this answers your question, but - when you drag and drop a set of photos into the web uploader, it should retain the order that they are sorted in the folder on your computer. So if you have a set of photos:
a.jpg
b.jpg
c.jpg
Make your folder sorted by filename, select all three, click and drag (make sure you click and drag from “a.jpg” and not one of the other files), and they should appear in that order in the web uploader.
There isn’t a way to autosort the photos after they’ve been uploaded, they have to be manually dragged around. (Or if you are combining multiple photos into a single observation, you can select multiple “cards” and then click “Combine”.) Here’s a related feature request: https://forum.inaturalist.org/t/sort-by-date-or-file-name-during-upload/1949/4