sergf That supports my assumption. You are using version 4 on a non supported macOS version.
You can try the tip suggested here:
https://forum.projectwizards.net/d/141-inspector-color-scheme-issues/2
And use the Inspector Position option Separate window
We recommend using the latest available Merlin Project Version - ie 9.0.3 - which is optimised for the latest macOS version.