You need to create a second project. But I’d create both projects with hierachical sheets. Top level sheet would contain only one subsheet. And in both project I’d link the subsheet to the same .sch file
Can you elaborate on that?
Footprints are usually attached to schematic symbols. I guess it can be done if you assign footprints in Pcbnew and then never update them during Eeschema -> Pcbnew.
Related to this: In Pcbnew Footprint info can be exported in a .dcm file, which can set the footprint info in the schematic.
You are right, I was too much fixed on idea of using schematics in two project and I forgot the emphasis that the footprints will be different. @iitgrad disregard my idea. Mea culpa.
There is a third option to get advantage of a shared hierarchical sheet.
Before, I want to say that I have never tried this option. In this case I finished the schematic for the THT layout, duplicated the whole project and assigned again the SMD footprints for the new layout.
@MitjaN’s idea can be achieved with .equ files.
An .equ file relates every symbol with its footprint and can be loaded by cvpcb.
So each time one wants to switch from THT to SMD (or the other way round ) the only thing they must do is loading the .equ related to the project.