For the Microsoft Store edition AND/OR Gamepass edition:
The path is: C:\Users\[YOUR USERNAME]\AppData\Local\Packages\Microsoft.FlightSimulator_<RANDOMLETTERS>\LocalCache\Packages\Community
For the Steam edition:
The path is: C:\Users\[YOUR USERNAME]\AppData\Roaming\Microsoft Flight Simulator\Packages\Community.
For the Boxed edition:
The path is: C:\Users\[YOUR USERNAME]\AppData\Local\MSFSPackages\Community.
It’s where all the community mods and addons go.