It is possible to upload the slot list created in Arma 3 in order to have the slot list generated automatically.
Upload of a mission.sqm
To do this, save the mission in the Arma 3 editor and make sure that “binarise scenario file” is unchecked. After that, the mission.sqm to be uploaded in the Event Wizard will be located in the mission folder. This folder is located under %USERPROFILE%\Documents\Arma 3 -> missions or mpmissions.