@uberprutser I'm now on a machine using stable. I changed my view settings to have the index left, message right like you (I really prefer the "horizontal" view with index top, message bottom view...) and changed the option to show filters as text (I have it set to icons). I still see the filters on the main mailbox selections:
e9a18350-8ff7-41a0-98d8-03ca17610f6b-image.png
I have no idea why you see something different. This is Vivaldi 6.2.3105.51 (Stable channel) (64-bit)
Edit: I captured the screen highlighting "all acounts" to cover my mail addresses - so it's showing "no messages"... but I get the same filtering available for all views of all accounts