While there might not be an addon that perfectly emulates every feature of Toby on Firefox, I am fully confident you can achieve all of its features with settings, config/userchrome edits, or some of the addons that are available. Personally I use Tab Session Manager and Tab Center Reborn (heavily edited though), so you might look into those and see if they have features you like.
If you find anything similar to the Toby extension please let me know. I haven’t been able to find anything close on Firefox.
https://addons.mozilla.org/en-US/firefox/addon/toby-for-tabs/
For a similar project that is open source, check out https://josh-berry.github.io/tab-stash/
I expect you have tried to search for it in Firefox, but have you tried sideloading it somehow?
As far as I know Firefox supports a superset of the APIs that Chrome support, so it should be a possible?
While there might not be an addon that perfectly emulates every feature of Toby on Firefox, I am fully confident you can achieve all of its features with settings, config/userchrome edits, or some of the addons that are available. Personally I use Tab Session Manager and Tab Center Reborn (heavily edited though), so you might look into those and see if they have features you like.