I would love a section on the main page that showed series I am currently reading. Eg. ***** Series - 3/5 books read.

Plus an option to DNF series if we don't plan to finish them, and a pause option so they don't show until we start them again.

Would love an overview of all the series I've read and started, and maybe also mark a series as DNF even when you didn't DNF in the middle of a book

I’d love a filter that is for book in a series in addition to the filter for books not in a series so that I could see what series I read and check for new books. I think the recommendations only work if you added the following books to to read. It would be nice to see ones I didn’t know were published.

Also maybe a part of the recommendation section could be an “up next” in series you have rated books highly.

Yes please, more support for series tracking in all the ways

Better series support would be lovely.
Related to this, being able to filter my To-Read-Pile by "Books that are part of a series" or even better "Books that are next in a series" would also be a great help.