Our package in Salesforce has extensive user documentation.
As we prepare for the transition to Lightning we are searching to find ways to keep the documentation near the functionality it documents. This is vital for keeping support costs down.
Most of our clients are going to look for help first in the Lightning contextual help menu:
As is, clients will look in this section and only find generic Salesforce help which is an undesirable situation for us.
The problem is this menu does not seem to be customizable, which seems like a huge functionality gap on Salesforce's part.