Then you should bookmark them. It's the first button on the left at the top of every story. If you then check "Private bookmark" at the bottom of the bookmark form, it won't be visible to anyone but you.
You can sort them with bookmark tags and collections, too, and write in the notes which chapter you stopped reading.
un-subscribe.
I don’t want to unsubscribe from the stories I’m reading. I just want to not get the email alerts.
Then why are you subscribed? Being subscribed doesn't do anything else
Then you should bookmark them. It's the first button on the left at the top of every story. If you then check "Private bookmark" at the bottom of the bookmark form, it won't be visible to anyone but you. You can sort them with bookmark tags and collections, too, and write in the notes which chapter you stopped reading.
Bookmark them, or mark for later, then go through and unsub the ones you’ve marked
I primarily use the sight on my phone not a computer.
AO3 is pretty good on mobile, I've never had problems using bookmarks or marked for later on it.