Fusion can load a local STEP to make a new design
Fusion cannot insert a local STEP file in an existing design
Fusion cannot insert a cloud STEP file into an existing design
Fusion can insert a cloud design in a new design
Fusion cannot insert a cloud design into a base feature in a new design
Fusion cannot insert a cloud STEP into a base feature in a new design
I know nobody that uses DXF - I never even came across a person in industrial design.
We use STEP!
I have to say I am stunned that after years of asking for better data import Fusion is still the
only application that fails at offering those must have structural tools and functions.