Does not do what is promised.

Not working. Period.

"Vivaldi stack" feature, lets you select tabs and stack them in a group. This addon stacks tabs from 1 website (i.e, YouTube). Bad description and it's not what I'm looking for.

While I admire the effort to provide a function similar to "tab stacking", this add-on isn't true to it's name. It does not implement or emulate the feature found in the other browser. Very misleading. Grouping tabs by domain using the context menu is not tab stacking.

this does not cover the vivalid stack feature...

It doesn't stack tabs from different domains.

Do absolutely nothing.
In short, doesn't stack tabs as Vivaldi is able to.
To avoid, so.
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Ne fait absolument rien.
En somme n'empile pas les onglets comme peut le faire Vivaldi. A éviter donc.