SSM has a feature where you can choose what footage to export from multiple cameras on multiple devices, add it to a export queue and then schedule this export to occur at later time and date.
Firstly, add the camera(s) to a viewing pane and click on playback, then click on the export button and choose 'Export one-time schedule'
All cameras in the current layout will appear in the one-time schedule box:
Select the first camera (multiple cameras can also be selected), set the time and date of the start of the export and the time and date of the end of the export along with the format type and the the path to save the export to, then click on Add:
You will then see in the Schedule list mode, the camera the date and time of export and format
Repeat for other cameras in the list:
Then set the time to schedule the exports, select all cameras and click Apply:
At the scheduled time the export will be performed and the files will appear in the export path once the export if finished: