On this documentation page : https://documentation.bonitasoft.com/bonita/7.8/expressions-and-scripts
The item "Manage Groovy scripts" is no longer available in the "Development menu".
I think the documentation need to be adapted the new way to accede Groovy scripts.
Bonita studio community 7.8.0 on Windows 7
Scripts are still visible in the project tree (as explained in ) and can be created with a right click on "My Project" then "New > Groovy class".