1. The Marketplace technically doesn't support the base pack+expansion i.e. "product family" concept which CS has been using for more than 20 years. That's why ALL marketplace aircraft are standalone products.

2. In CS store, we have tried to continue the base pack+expansion thing, which  saves our customers more than 50% on each expansion.

3. Pilot release of the first 3 expansions (767-300ER GE, 777-300 PW, 777-300 RR) proved that was a bad idea.
So no more new "base pack+expansion" releases for the MSFS2020 in CS store.

Each of the 3 available expansion has the following warning:
WON’T WORK WITH THE 7X7 AND LIVERY PACKS FROM MARKETPLACE!