So I originally played on the PS4 and own the base game plus the year 1 pass. So I have expansions 1 and 2. I came back to play when New Light started and enabled cross save of my PS4 account. When I play it on the PC, it shows I have access to both of the expansions. I want to purchase forsaken and shadowkeep but am unsure if I purchase it on one platform will it carry over like expansions 1 and 2 did. I searched around on these forums and never really found an answer.
Sorry but no. Forsaken and Shadowkeep are only available on the platform you buy them on the licences do not move with the characters. The reason you got CoO and Warmind as all year 1 stuff including the dlc is part of the New Light pack.