I have implemented a Mondrian Easel based on Glamour. It is available in the latest Glamour-Tools. I attached here a screenshot.

You can spawn it via something like:

GLMMondrianEasel openOn: {#classes -> Collection allSubclasses}

The only thing it does not offer is completion, but this is because it is not yet supported by Glamour. Alex, I know you implemented it for the Easel. Would you have time to look into having it in Glamour as well?

Cheers,

Doru