This might be considered an exploit or glitch. I'm not the one to discover it. Probably some of you know this already.

You can transfer ALL of your Expedition items to your main save.

Step one -- complete the Expedition. But don't accept the End Expedition dialog when it pops up (ESC on PC, O on PlayStation, etc. -- basically, dismiss the dialog without hitting "Accept").

(A) Go to the Expedition terminal and fill up all the inventory there with stuff you want to transfer back to your main save. DO NOT CLICK END EXPEDITION.

(B) Get into and out of your starship to create a save, then using the game menu choose "Return to Primary Save"

(C) In your main save, collect all the Expedition items from the Expedition terminal. Then click "Resume Expedition" from the Expedition terminal.

(D) Go to step (A) and repeat until everything is transferred.

This is great if you want to collect things like technology modules from destroying frigates/freighters or something in your expedition save (to send back to your main save) without having to deal with the faction hits. Or whatever else you wish to farm from an expedition.