Keeping modifications when going live

Hello,
I really liked being able to work on a new theme for my site while the old was still active but now I am ready to switch the active themes for the general public. When I did so, the theme that I had been working on did not save many of the modifications I had made (ex: header image, font customizations, footer widgets, navbar customizations).

In fact, it seems to be most of the modifications I made with the customizer.

Is there a way to make all of my modifications move over when I go live?