By default, results from S3 are ordered alphabetically and the protocol itself doesn't support any ordering.
To implement custom orders, we can fetch all of the results and expose sorting options to the user. Ordering would happen client-side.
UPDATE:
This is now implemented in 1.5.3 version released on all platforms (except iOS which waits for an approval).
Once you choose sorting mode you're prompted to switch to: "cached mode" which relies on a local file index. If it's empty it needs to be built, if it's not up to date you have an option to regenerate it.
This index is shared with search function, so after using ordering function the search will work immediately and vice versa.
Soon we plan to implement diff update, which wouldn't require full index rebuild in order to include recent changes: https://s3drive.canny.io/feature-requests/p/implement-searchorder-index-diff-rebuild
Please let me know in the comment or Discord: https://discord.com/invite/YvxvypRqCu if that works for you.