updates and customizations

This is not a problem query it is a question about something that works with Picolight!

I have applied your updates (twice) and the theme stays happy and healthy! All customizations are saved.

On another theme I always lose my header. I do not have a child theme ( i am a little fuzzy on the topic)

Is there a coding that you use that protects customizations from being lost?
Thank you for your time and energy, it truly is appreciated! Mary