How to reset last-seen-post cursor

I use the unread feature to track long threads I’ve already read part of. So I might first notice a thread with 150 posts. I might read 20, set it aside, read 20 more two hours later, etc. Conveniently, Discourse remembers where I’d left off shown with the “last visit” line. And I can jump there with the Shift+L command from anywhere else in the thread. So far, so good. But how can I reset that last-visited point to “nowhere”? Or to “here” for whatever post I happen to be looking at?

Here’s the use case. Let’s say the thread has 150 posts and I’ve read down to #50. Then I leave the page for some other thread. Then I go back to the thread which now has 152 posts. Shift-L takes me to post #50. Excellent. Works great.

Now I screw up and hit [End] and now I’m down looking at post #152. A few seconds later Discourse decides I’ve now seen the whole thread.

So now, #152 is my Shift-L point. I’m not asking how to recover my old last-seen-post # of 50. That’s gone. I just want to reset the last-seen-post to post #1. Then I can find my own way to post #50 and then progress normally from there in stages.

Bottom line, I want a way to recover from mistakenly moving the last-seen-post point way past where I’ve actually read.

I tried reseting “tracking” to “normal”, clearing cookies, etc. No help.

Any ideas anyone?