Apr 25 2020 10:36 PM
Apr 26 2020 01:04 AM
Apr 27 2020 06:27 AM
@AnaUser There is no masterpage for Modern Sites. It's also not recommended or supported to change the layout of a modern site unless using the provided modern page layouts/sections.
Given the screen shot you provided, it's going to be difficult to do what you want to do in a Modern Site in a supported way.
Apr 28 2020 05:36 AM
@AnaUser My recommendation would be to go back to the customer and work through mockups that are supported in the modern environment.
However, if you are hard set on implementing something like this in the mock up, the docs.microsoft.com site has all the resources you need. Be prepared, it's A LOT of reading. Also note, that not all the information is going to be on this page, but you'll to click through the links in the Terms and Concepts section, to get a full grasp of what you are trying to do.