Updating my browser apparently caused extensions to get updated as well. Now uMatrix 1.1.2 is installed. The config box is very small compared to the size available to the browser window area. You have to scroll horizontally to reach the columns on the right, and the name of the 3rd party entity scrolls out of the window. This makes it inconvenient and cumbersome to alter the settings.

I suppose this change was motivated by complaints that the config window was too large on small screens:

https://github.com/gorhill/uMatrix/issues/483
https://github.com/gorhill/uMatrix/issues/683