Yes

You need to be in the same approval group to be able to collaborate on a risk assessment. If you are, you can see all your group's risk assessments in the drafts tab.

Click actions and edit and you will be able to work on the risk assessment

You can work on different aspects, but the limitation is that you cannot do this simultaneously. One person can work on it and save, then the next person can work on it and save.

Concurrent editing is not available.

The moment you edit a risk assessment you're automatically added as a contributor

If you sat next to each other and worked on it together, on the final summary screen you can add yourself as a contributor

The audit trail shows who worked on it together, rather than who wrote each specific part

The original creator/owner of the risk assessment still needs to submit for review or approval

If they are not available the day it needs to be submitted, the risk assessment can be reassigned to another member of the approval group and they can submit for approval