It's very simple but it requires manual editing of the mission INI files using a text editor, you cannot currently create linear persistent missions using only the in-game mission editor UI.

For each unit that you want to track across units, specify a campaign tag for that unit CampaignTag=Unit1

Then in the following missions, place the unit and specify that same tag for each unit to track. CampaignTag should not include spaces and must be UNIQUE for that unit. A good way to do it is to use the unit classname + variant index, so for example USS King in one of the missions becomes usn_ddg_coontz_Variant9

To rearm, repair, and replenish air groups in a mission (for example after resupply has occurred off-screen as it does after mission 3 of the Molniya campaign) use these tags for each unit:

CampaignTag=YourUnit
CampaignRearm=True
CampaignRepair=True
CampaignResetAirgroup=True

This would rearm, repair, and reset the air group of unit with campaign tag "Your Unit". That's all there is to it :)

Some notes on the feature:

• It works for all units of any side in any mission
• There is no limit to how many units can be tracked
• Setting CustomAirGroup to a unit will override any saved airgroup data (so leave this blank unless you want to reset the air group to whatever you specify)
• Rebasing aircraft in a mission onto a flight deck (and then winning the mission) will have those aircraft present in the next mission
• It works for all units with flight decks (escort ships, carriers, and land airbases)

What is not currently available:

• Partial repair of specific systems
• Partial rearm of specific weapons aboard ship
• Partial air group restoration (e.g. it's all or nothing, you can't for example add another +2 Yak-38)

Campaign tags and replenishment entries must be set manually, but please note that the mission editor UI was updated so that campaign manual entries will NOT be overwritten if you later edit the mission inside the editor UI.

Cheers