It's not possible to change video resolution during a video production

You must determine settings for video production prior to beginning the project.

It's not possible to change video resolution settings while recording a video production. That's to prevent errors or unexpected results.

If, after beginning a project, you decide that you want to use a different video resolution setting, then your only choices are keeping the current settings, or closing the current project and creating a new one with the video resolution settings that you want.