brent Are workspace cookies separated like containers?
I think the cookies are all one common collection (which is what I would prefer). Looking at the number of saved cookies in each of the three Vivaldi instances, I find there are 312 of them from 94 domains. Actually 313 from one of them, but 312 from each of the other two. I suspect that the 313th cookie is something newer than in the others.
Since I block ads and trackers, I believe most of the saved cookies are ones that identify me to my stock broker, my bank, stores where I shop, and publications I subscribe to, so I'd want those to be available regardless of which instance I happen to be using. Looking at the list of saved cookies in one of the instances, there appear to be cookies saved by the other instances.
One thing that bothered me was a cookie I noticed from twitter.com, where I don't have an account. I'm going to need to give that list a more serious examination soon. Although I did have a Twitter account at one time, much more recently I deleted all my cookies while debugging a problem that I thought could have been cookie-related. So whatever is there now has been added long after I left Twitter.
If each of my browser instance had its own independent cookie collection, I'd need to be very careful not to ever use one instance for domains delegated to another instance. I wouldn't find that very useful.