I created a child theme from the delicate theme, all I needed for the child theme to show up was a new folder (delicatechild) and the style.css and it showed up for me in the admin.
One thing that did confuse me though at first was because all the theme description information was the same, I thought it wasn’t showing but then I realized delicate was my current theme and the child theme was indeed being listed below.
On thing you can do to separate the child themes visually in your admin is to edit the header comments of the child theme style.css file, which is what I did to the delicate theme. The original had the following:
/*
------------------------------------------------------------------------
Theme Name: Delicate
Theme URI: https://www.nattywp.com/view-natty-theme.php?theme_id=99900&theme_name=Delicate
Description: Delicate is a free professional WordPress theme built on the NattyWP CMS framework.
Version: 1.0
Author: NattyWP
I changed the Theme Name to:
/*
------------------------------------------------------------------------
Theme Name: Delicate Child
Theme URI: https://www.nattywp.com/view-natty-theme.php?theme_id=99900&theme_name=Delicate
Description: Delicate is a free professional WordPress theme built on the NattyWP CMS framework.
Version: 1.0
Author: NattyWP
So now on the admin side it shows Delicate Child as the title, so I know which one I am working with lol