As mentioned in the technical issues section the tool UI is not going to be placed the same way on all resolutions and/or UI scales (some minor visual differences may also appear). Works best with UI scale small and very small, of course on 4k/UW monitors that most likely extends to larger scales as well. Or doesn't work at all, who knows..

1920×1200, UI scale small:

1920×1200, UI scale very small:

With some setups the tool UI will block the Eden sidepanels, 1920×1200, UI scale normal:

The tool features a setting that will force the tool UI to automatically “dodge” Eden side panels when moving the mouse cursor over either one of them, the setting can be found in the Prefs leaf, and as explained there it's called Auto-hide tool.
Checking the Auto-hide tool box will make the tool fade in/out when you move the mouse cursor over either one of the Eden side panels. This of course prevents you from accessing the tool properly so if you hold down CTRL on your keyboard when entering the panel areas it will disable the “dodging” as long as you keep CTRL down. Once you release it the dodging goes back to normal.

The other way to get around this is to use the hide/reveal tool UI kb shortcut, CTRL + BACKSPACE.
As explained earlier using that shortcut you can hide/reveal the tool UI willy nilly.