I just started at a new company with multiple WordPress sites and none of them use child themes.
I've seen posts here about using comparison scripts to compare the files to a fresh version of that theme, but I'm not too familiar with scripting and no one even provided an example of how to do that.
I'm also wondering how I would go about getting all of the other settings inside WordPress to carry over (theme customizations, homepage settings, etc.). I know on some themes there can be a lot of drag-and-drop type editing that you lose when moving to a new theme. I already made that mistake once here and had to quickly change it back to the parent theme.
TL;DR
How can I create child themes and keep everything looking the same as parent themes that are already active?