More receive addresses with electrum I cannot find any documentation or an option anywhere in the electrum client to put it into expert mode. I'm not even sure it can be done any longer, and it is important I raise the gap limit. It like chasing after a myth.

How do I put it in expert mode? Why has that been made so difficult? It seems against every principle of free software.
There's no Expert Mode anymore. The Gap Limit has been hidden from the UI as it was unnecessarily complicated for normal users, and it is not a good method for merchants.

If you need to change the gap limit, enter this in the Console tab and restart the client (Tested with Electrum 3.0):

wallet.change_gap_limit(10)
wallet.storage.write()

To view/verify the current gap limit, type the follwing in the console:
wallet.gap_limit