Sometimes, when selecting the color of an object in the Editor, upon clicking "Apply" the Editor window drops to the back of all open windows (hidden). It does not appear to minimize because clicking the icon in the Task Bar animates it to minimize. Clicking the icon a second time brings the Editor window back up. This has occurred when modifying the color of text, arrow, line, box, free draw, and circles. I haven't been able to tie this to a specific set of circumstances yet and it occurs inconsistently, seemingly at random depending on the session. It does seem to be consistent within a specific editing session.
Windows 10 Pro 64-bit Version 1809 running on a Lenovo Thinkpad P51