Same request - being able to group tabs the way you can in Chrome browser (no need for extension, it is now part of Chrome functionality). With few adjustments to Fred's suggestions:
1. To be able to select any of the already opened tabs and add them to a new group. This will NOT create a new collection automatically.
* Additional functionality would be to allow for saving the new group as a collection if needed.
2. Similarly to Chrome, one can expand and collapse the group by clicking on its name.
3. An option to click on existing collection and opening it as a new group (such that all papers in the collection are the tabs in this group).

I think this functionality would be very helpful when you are working on a project and you need certain papers that are scattered across different collections. Right now you want to group them all under a temporal topic, but you don't necessarily want to save them as a collection.

Here is a script^[1] I have been using for a while to save and restore tab groups in zotero. Check it out if you are interested.

[1]: https://gist.github.com/ifree/a91b68dbe1a6927bd9fd8ba4b67aad6a

@superheldinnr1
The return value is a bit confusing indeed, you could just ignore it(Because there is no function call or variable definitions). To load/store tabs groups you can clear developer console and call one of the functions you've just defined eg: `save_tabs_to_selected_collection`, `load_tabs_from_selected_item`.

ps. I have a forked version of Zutilo you might interest: https://github.com/ifree/Zutilo

Hey, not problem, this is a step-by-step guide,
1. open zotero developer console (Toolbar: Tools/Develper/Run Javascript)
2. paste code from [here](https://gist.github.com/ifree/a91b68dbe1a6927bd9fd8ba4b67aad6a) **and** hit run, (skip if you have done it before, you need to execute it if zotero is relaunched)
3. clear the developer console(the text area)
4. type/paste save_tabs_to_selected_collection() **and** hit run
5. the tab groups are saved in your active collection folder

it's a bit tedious /facepalm, I recommend you to use my forked extension if you heavily relied on the tab group funciton.

/facepalm, sorry for that, it seems once you cleared the console, previous function definitions are gone. So you have to
1. paste code from [here](https://gist.github.com/ifree/a91b68dbe1a6927bd9fd8ba4b67aad6a)
2. type/paste save_tabs_to_selected_collection()
3. hit run

btw, you could install the addon I made for convenience https://github.com/ifree/Zutilo/releases/tag/experimental

Here is the instruction I've recorded for you : 

Thanks @ifree, I implemented one with the plugin Actions & Tags (https://github.com/windingwind/zotero-actions-tags), without the need to use a custom build of Zutilo, and works for Zotero 7:

https://github.com/windingwind/zotero-actions-tags/discussions/129

Do the steps only once:

1. Install the latest prerelease Actions & Tags for Zotero 7 (https://github.com/windingwind/zotero-actions-tags/releases)

2. Goto settings -> Actions & Tags -> `+` button to create an action

3. In the popup, set `Operation` as Script; paste the code from this link (https://github.com/windingwind/zotero-actions-tags/discussions/129) into `Data`; Click shortcut button to record a shortcut. Click save


Use your shortcut to trigger the action (Press OK to save tabs, and Cancel to restore tabs).

I wish this group function too, as this helps me arrange what I am reading.

Tab groups are planned. No need to request them.

+1 for tabs grouping feature