100% support this feature. I find the current panel/dock setup fairly limiting. The way RoamResearch did it was, for me, incredibly productive. You could easily open any node in the right sidepar/panel. They were collapsible, sortable, etc.. You could do anything at any time without moving away from your main content/panel. This helped a lot with navigation and avoiding context switching. I understand it's a personal preference, but this is the biggest thing I miss from Roam, especially now that I can't seem to get stacked vertical panels in Tana's right dock.
How it looked in Roam:
I did like Roam's implementation a lot! But I do like the feature of having more than two vertical panels too. So some kind of a mix of that flexibility.
Roam made it possible to make any node the main node with a click of a button iirc. This is possible with Tana too, but not without losing all other panels.