This is a two-in-one idea. I realize that "undo in change parameters" was already a suggestion, but that was over two years ago, and I have a second part to this.
1) I think it would be great to have undo and redo support, especially via the standard hotkeys (control-z and control-y respectively), so if you're in the Modify -> Change Parameters window, you can make a change to a parameter, and then, when you inevitably select a number that's wacky, you can just control-z to undo, and be right back where you started. A lot of designers keep their eyes on the design side of the screen to see how a parameter change impacts the design, so they may not even know the original value of the parameter. Undo would make a lot of designers' lives a lot easier.
2) Just like the Sketch Palette is docked when you're in Sketch mode, I'd like to see the Parameter window be a floating/docked window that can be up at all times, or at least turned on and off. Fusion 360 is a parametric design tool. I feel like the parameter window should be allowed to hang out in the forefront, so we can enter parameters while we're designing, not going into a menu, making a change, then exiting, continuing the design. If this window were dockable/floatable, it could (if the user so chooses) sit on-screen, even taking the space of the "browser" area on the left-hand side of the screen. When I'm working on a project, I'm focused on that singular project. Maybe other people like to browse while they design, but I don't. It seems distracting. So, perhaps when someone's actually working on a design, the "file browser" could take a backseat automatically, and the parameters window (or something else? User's choice!) could take up that valuable real estate.
Thanks guys!