Yeah, I knew about the unavailability of Tabstash, which is unfortunate. It would be the best option. However, I learned something about Onetab today - I thought it was strange that you couldn’t get it to work, when I used it just the other day on Android. But if you look at the FAQs in the Details section (see attached screenshot), it only can save the ‘active tabs’ as dictated by Firefox Mobile, so in that sense it’s not ideal.

Tabstash would’ve been my initial suggestion, but it doesn’t seem to be available for mobile. Onetab was what I ended up using when I wanted to do something similar to what you’re wanting to do.