I read the whole documentation of Mongo Atlas Search and I still don't know if there is operator "greater than" for strings. I'm trying to implement my own "search_after" in the query because sort+skip is not a good idea and every time I google for a feature I end up in a forum where a PM says "Coming soon, we will prioritize this" and I know that things don't work like that

I do not think there is an greater than for strings since it could be ambiguous.

Should a longer string count as bigger than a short one of should it be case sensitive or not and what about unicode chars.

Sort already have that support.

Adding this into a greater than is probably complex since the framework around greater than probably is not designed around it.

For example, if the string id thousands of chars long, should all of them be loaded in memory?

In those cases a pre sorted index would be very helpful for performance.