So, I have the standard edition of the game, and I want to upgrade it to Deluxe edition. Unfortunely, I can't. I submitted a ticket about it on Steam, they gave me this answer.
How can I purchase Deluxe edition without paying what I got again?
Here's the answer Steam Support gave me:
Please do know, we do not offer package upgrade, exchange or refund the difference for any games purchased on Steam.
Unfortunately, since you already own the Deluxe version of the game you can no longer purchase the Operator edition.
The only way to purchase the Operator edition is to refund your initial purchase. But, your purchase does not qualify for a refund.
I highly recommend to contact the support team of the game, and ask them if they can provide a possible upgrade option.
How can I purchase Deluxe edition without paying what I got again?
Here's the answer Steam Support gave me:
Please do know, we do not offer package upgrade, exchange or refund the difference for any games purchased on Steam.
Unfortunately, since you already own the Deluxe version of the game you can no longer purchase the Operator edition.
The only way to purchase the Operator edition is to refund your initial purchase. But, your purchase does not qualify for a refund.
I highly recommend to contact the support team of the game, and ask them if they can provide a possible upgrade option.