I have read a few of the older posts and can't seem to find the answer to this problem.
I have installed the plugin in mu-plugins. I have added the rules for custom_content_dashboard_widget to appear in top right. It displays in the correct new position in my main site dashboard.
However, when I go to the dashboard of my test sites it hasn't moved and is in the default position. I refreshed my site many times in case it was cached.
Update: If I log out and log in as a test user it is correct, just not showing when I as super admin user visit the site back end. So not such a biggie then, but would be better if it displayed correctly when I visited as admin.