1. I add new Filter Layer (HSV/HSL Adjustment) 2. I open Filter Layer's properties (via context menu or F3) 3a. The popup appears in the middle of the screen, covering the canvas. It's unmovable, I can't drag by it's title bar to move it somewhere else. 3b. When the popup appears, it darkens all Krita window, including the canvas. It's hard to adjust colours properly while having the canvas darkened. I'm using Ubuntu 17.10 (x86_64) release 4.13.0-16-generic and have krita's appimage (there's no such option on the dropdown list) I think it might be related to Ubuntu's switch to Gnome Shell.
That's a problem with the window manager. We cannot do anything about that. It's an ordinary dialog, marked as a dialog, but Gnome thinks it's being smart...