It's quite strange. Now I have just tested it with other browsers and did not work, tried on Linux and Windows.
But I remember some time ago that the video position was stored when I watched it from my mobile and from my desktop, at least on Edge that is the one I used to use before.
Anyway it looks like it is more related to the YT account than the browser.
Just FYI, that's not the number of closed "tabs", rather closed items. If you close a window it appears in the trash bin, and it can be expanded just like a stack, and the total number of tabs can then exceed 25.
@Cqoicebordel it's not only cosmetic, as you can disable or enable blocking per specific (or general) local pages. The only possibility is to disable or enable blocking settings browser wide (from the browser settings).
You can not use Google Keep with Vivaldi because the extension uses Google Sync and other services.
Vivaldi has no contract with Google to use unpaid or licensed access to Google Services.
The extension is incompatible as listed in https://forum.vivaldi.net/topic/8129/list-of-incompatible-extensions