This issue has been closed as 'Won't Fix' due to an extended period of time without updates. If this issue is important to you please let us know by posting on the AnswerHub or UDN, and Epic will re-open the ticket for further review.
It looks like the Functions Get Float Parameter, Get Vector Parameter, Get Actor Parameter, Get Color Parameter are listed in the API, but are not callable in a Blueprint.
RESULTS: Functions are not accessible in BPs
EXPECTED: Functions should be accessible.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-19606 in the post.