RE: Shortcut assingment
I think File/Document Setup......is the closest you will find (useful) for updating a viewport on a locked layer.
This of course still requires you to make the additional selection of pertinant model reference(s)..........and of course select Update.
Unfortunately there is not a shortcut option for File/DocumentSetup/Reference(s)
(I wish there were!)
Re: File/Update Document
My guess would be you must have a specific document in the LO file selected "prior to" for this to have any effect.
Best,
Charlie