On any website, as long as the tab is the last one in your list of open tabs,
clicking on a link will open it in another tab, while creating a new group.
(As long as the tab is NOT the last one in your list of tabs, clicking a link simply opens the link in the same tab like normal.)
Then close the browser and open it again. The group that was created will have been deleted with the tabs in it.
I dont understand the tabs on android man. I swear when i want them to open in a same group it will work sometimes and other times it just opens a new tab. Ive given up with trying to figure it out. I havent noticed this particular issue but i dont doubt it. Ive noticed a group of tabs being completely ungrouped and opened in their own groups after closing the browser. Tabs that ive had grouped forever and were the only ones i would leave open as a group and never add anything else to that group.
Oh yeah, that also happens often.
Ill just open brave and ill have 120 or so ungrouped tabs
Damn, that’s a lotta tabs!! Ive never had the issue on desktop, only on android. Hasn’t happened in a little while but now that I’ve said that it will probably happen again. Which version are you using?
Bit of an exaggeration, but i do keep 40+ tabs open I regularly visit 
Im on Brave 1.78.102 using Android 14
Jeeeez… 
that is quite a few but believe me, I know how it happens!! I TRY my best to keep it limited and I like to clear cookies often. I have it set to clear on leaving the site and on browser close. I’d be a liar if I said Ive never caught myself having 30 some odd tabs open. Until I say “whoa, what do I got going here” look back earlier tabs and realize why they are open but then looking at the more recent ones, I’m on the same damn sites 
Some I keep open to avoid relogging in, so sometimes I won’t shut down the browser but i want to get rid of the cookie files. I wish there was a way to multi select websites (on android) to clear out a bunch all together and keep a few. On Android, you need to go select each one, the click delete then confirm. I don’t like to whitelist because there’s times where I do want everything cleared. That and a few other things are what I would love to see in the browser (more control for the blocking element feature, along with a hotkey for it on desktop, like it is in ublock alt+x). Sorry for the long ramble tab master!! 
Cheers