I am trying to make an Alternate Layout. I followed the instructions in this video whereby I start with my original layout, go to Layout > Create Alternate Layout … and use the settings shown in the attached screen capture. The alternate layout gets made fine but when I make edits in the "parent" layout they aren't reflected in the "child" layout. I've tried this with ID 2020 on two different OSs (High Sierra and Big Sur). What am I doing wrong?
Alternate layouts don't update that way. Once created they are fixed, except maybe the linked textframes you already discovered. Depending on what you're doing, master spreads are more suitable. And use object styles – they allow you to later edit all objects in one go which have that style applied.
So, I answered part of my question. I was led to believe the change would show on the actual text box when, in fact, I had to go to Window > Links and click on the warning icon for the text to update. Is there are way that I can update things like background colours on boxes or add elements after the Alternate Layout has been created?