I work across 4 workspaces on Win 10 and probably have 30-40 Opera tabs open at a time over 4 instances of opera, one per workspace. One and exactly one panel needs the side bar off so that I do not have to do horizontal scrolling on a data set.
When I turn off the side bar it gets all of my panels across all of my workspaces. I like the side bar and just want to get rid of it on one panel. If there isn't a way to do this, could it be added in a future release?