Hello Mathieu, I think the problem got fixed, however not in an elegant way. The solution is to manually set cmake var BUILD_SHARED_LIBS to ON in the top level CMakeLists.txt. Like this:
Then the build project will generate .dll file correctly as I wish. The keynote turn out to be that once a Plugin gets built as a solo project, instead of part of the ParaView project, this cmake var will be disabled somehow(it doesn’t appear on CMake GUI variables lists anyway). Maybe there is another way for paraview to fix this, but this just works.
And I found another topic quite similar to mine——Build a plugin from examples.