Genesis (and others like it) has always had a problem with a lack of consensus on how to cope with updates to its child themes. The simple conventional answer is that you should seldom or never update them, because it may be a very time-intensive process to avoid breaking things. StudioPress does not do auto-updates for child themes anymore, so you have to go out of your way to follow the updates, get them, and merge the changes into your existing child theme. If you do this through a git repo you can automate and manage it rather simply and well. But even if you are doing that, why make things any more difficult than necessary?
My advice:
- DON’T try to make a grandchild theme. Nobody recommends this.
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DON’T make m/any changes to a Genesis child theme. The fewer changes the better, preferably zero. Then you can run updates to it without worry.
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DO all your customizations in additional CSS outside the child theme. Add it to the Customizer if you like, just back it up carefully or lock out people who you don’t want touching it.
- DO further customizations in original plugins or snippets.
- DO use Genesis plugins like Simple Hooks and Simple Edits.
If you are switching between parent/child themes your widget and customizer settings will not carry over between them. You need to use import/export plugins for that.
If you are making your own Genesis child:
- DON’T use @import for your CSS.
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DO use the enqueue method to include styles. š Covered in this good tutorial on the 2017 core theme.
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DON’T copy the parent theme’s
functions.phpor template files. If the same function is loaded twice it will throw a big error right away. - DO modify the parent theme’s
functions.phpwith additional code in your childfunctions.php. This is explained in the “Usingfunctions.php” section at the end of this excellent article. This is also an outstandlong long introduction to coding a child theme today.