How can I switch child themes from my theme's sub-folder?

Hi,

I tried the advanced theme switcher, but it does not work with my setup.

In my WP I have a themes folder as usual, but after I activate a theme I have an internal folder where I keep my child themes. ex. wp-content/themes/great-theme/themes

Is there a way to change this plugin to select the child themes from my internal folder?

Or, is there any recommendation for some other plugin/method?

Thanks,
MJ