When feeding a 'Static Bool Parameter' through a 'Quality Switch' node within the material editor, the material instance for said parameter does not appear until the 'Params' button is enabled.
If you instead remove the 'Quality Switch' from being fed with the 'Static Bool Parameter', then the parameter shows up as expected in the Material Instance.
I entered this bug as it spawned from [Link Removed]
It was bounced back and forth if this is the expected behavior so we wanted to enter an official bug report as a final answer is needed. This originally spawned from a UDN as well which has been resolved.
1. Open attached project
2. Open the 'M_Quality_Inst' material
3. Notice how the 'Static Switch Parameter Values' section exists, but does not have the parameters exposed to edit by default.
4. Click the 'Params' button.
Outcome The Static bool parameter appears
Expected The Static bool parameter appears without needing to press the parameter button.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-30327 in the post.