I also agree that this is an interesting proposal. If this is implemented, I personally think it would make more sense to mix menubar and toolbar actions together with adding sources/filters. As a longtime ParaView user/developer, I know the difference between showing a contour and showing a volume rendering. But that is a distinction that may leave less experienced users confused where to go and requires extra thought for those experienced users. Besides, adding filters is part of the menubar, so why not have them together?
I like the analogy with the vscode command bar. I use that a lot. However, I don’t think the distinction between “select a file” and “execute a command” in vscode is quite analogous to the distinction between “add pipeline object” and “do GUI command”.
More generally, vscode is separating “go someplace” from “do something”. The “do something” in ParaView would be the combined add filter + menu items + (many) toolbar buttons. The “go someplace” might be to find a parameter that can be manipulated. For example, if you typed “opacity”, it would quickly take you to the opacity display parameter of one of the existing pipeline objects. I don’t know how that would work, but it would be pretty useful. There was just a discussion at Proposal : Improve Properties Panels about how the search panel on the properties panel is useful but inconvenient enough that people don’t use it.