From the FX3 steam page:
I am very happy to bring you good news about one of the most discussed issues since we launched Pinball FX3. You have reached out to us about something that affected a number of you guys, and we’ve come up with a solution we hope can resolve this.
The completionists among you told us that you have had some trouble filling in your Pinball FX3 library with the introduction of table packs. For example, there was no way for you to purchase Rogue One without paying for the pack that includes Rebels, which you already owned and imported from Pinball FX2.
As of now, you should start to see coupons in your Steam inventory if you have owned certain Pinball FX2 tables.
You will receive an 80% pack discount coupon for each of the following tables:
Guardians of the Galaxy
Age of Ultron
You will receive a 75% pack discount coupon for each of the following tables:
Star Wars™ Pinball: Star Wars Rebels™
Star Wars™ Pinball: Rogue One™
Let me give you an example in the use of these coupons:
You owned Fantastic Four and Captain America from the Marvel Legends pack. You will receive TWO 80% discount coupons for the Marvel Legends pack. This means, you can buy the missing Doctor Strange table for a very discounted price and still surprise a friend with some great value pinball!
These coupons will be live for only three weeks, so make sure to use them to complete your collections!
We would like to thank you for your patience and your drive to complete your Pinball FX3 collections. And we hope you’ll have fun with the tables you haven’t experienced before!
All the best,