With regards to search, what term(s) were you searching for when you were looking for our Mobile Previewer? Using just the word “Preview”, the first selection in our search was the option I wanted. To test this out, I did the same on Unity’s Documentation and searched “Preview” and even “Mobile Preview” but was left in the same boat as you that it didn’t return the result I wanted.
We’re always happy to hear suggestions for improving our search and we are actively working toward improving this in the future for better discoverability of documentation.
For the C++ API this is also a large task that we’re working on, but it’ll take time. I don’t have an ETA really but it’s something that is requested often and something we’re aware we need to address.