You can link all campaigns into the grancampaign file , when one end , the next in order by victory condition 'll start....you have to know how to do it , so you have to learn how to do this....
You can edit all the single campaign in the grandcampaign and add also other campaign you/other have created , but you have to learn how....
Search online and in IL2 1946 related sites for tutorials...
I can suggest an older but still very informative tutorial about DCG and how it works created by Tailspin:
https://www.mediafire.com/download/huplrffmqz0ooxt/dcg_campaign_info_v321.zip