We have moved from On-Prem to Online through a migration, the designers have given us everything based on Classic Masterpages which includes custom design. I was wondering if we can carry over any of the existing design to the Modern look as we really like the new features available on the Document Libraries.
Or is SharePoint saying you can do one or the other but not both with the same design. So if we wanted some Site Collections to have Modern functionality, but other Site Collections to have the Classic Functionality is it possible to get them both to look the same with a custom design?
Also is there a graphical layout of the masterpage element id names that would make it easier to identify where to customise.