Lantern

I actually switched from Vivaldi to Zen (now on Librewolf due to inconsistent updates on Void) after UB0 was nerfed on Chrome.

Highly recommend either of these as an alternative, but having CSS/JSON knowledge is necessary if you want the exact experience you can get on Vivaldi.

“Just once” sounds like it opens the door for more than just once.

It’s also a really specific use case. I can’t imagine it being that useful to its target audience: authors. Ultimately, it relies heavily upon the premise of the user’s lack of self-control and does so to their detriment.

It’s less that you can’t, more that it would be impractical to do it.