This works for me:
1. Right-click the TopBraid Composer application to bring up the context menu
2. Hold down the Shift key
3. With Shift held, click Open in the context menu
4. This should bring up a dialog with three options: “Move to Bin”, “Open” and “Cancel”
5. Release the Shift key
6. Select “Open”.
I need to do this only the first time I start TBC. The next time, I simply double-click the application.
I have the “Allow apps downloaded from” preference set to “App Store and identified developers”.
I don't think I ever did anything on the command line to get these steps working, but maybe I forget something I did years ago.
Currently I'm on Catalina 10.15.6.
Richard