I am trying to:
Set parent layout for existing layouts
I expected to see:
"Set parent layout" button in the existing layout's hierarchy setting
Instead, I got:
"This layout displays in 'the content' area
If you want to design layouts for the entire page, you need to integrate Layouts into the theme"
without any option to set a parent for it.
Complete description:
I have previously created several layouts and decided to create one parent layout for them.
I created the parent layout named "Header & Footer", inserted a child layout cell, set it as a default parent layout. In the "Theme Options" metabox, I leave the "I will assign this layout to content later" option selected.
Next I edited an existing layout named "Home", expecting to see "Set parent layout" button in the hierarchy setting. Instead, I only see
"This layout displays in 'the content' area
If you want to design layouts for the entire page, you need to integrate Layouts into the theme"
This is weird. I tried again on my laptop at home and the Layouts UI works just fine, sort of.
It shows tabbed sections as expected. However, clicking the "Templates for Archives" tab does not display the list and the spinner next to the "Apply" button won't stop spinning.
I checked the browser's console and see a Javascript error.
FYI, all non-Types plugins and browser extensions are disabled.
I dirty-hacked the plugin to exclude posts with 'null' title. I know I should not make any modification on the plugin's codes, but I really need a quick way to be able to see the Layouts list.
Anyway, I tried your recommendation, creating new layouts and copy-paste the the codes from old layouts. It works. However, they could not completely unassigned. I unchecked all usages but still left with "Auto draft", making them unable to be deleted. Some even have "Undefined taxonomy archives" on their usages.
I think I'm going to start fresh, reinstalling everything, even WordPress. Had enough headache with old post types and taxonomies.