Two independent actions, deliberately so.
Generate builds the downloadable file from the values saved at that moment. You can run it as many times as you like, before or after Submit.
The button is named after what it produces, so it differs by report type: on EBA reports it reads Generate report package, and on Finansinspektionen forms Generate submission file. Same action, different output format.
Submit seals the report in Sigill. The institution's details are frozen onto the report — LEI, institution number, home country and reporting currency — and the grid becomes read-only. It cannot be undone, and you must type submit to confirm. It requires review permission.