How to move page template files like page-{slug}.php to a sub-directory?

I want to move page template files like page-{slug}.php to a sub-directory within my theme, in a way that WordPress will recognize them automatically. If the page templates of the said form doesn’t exist within the sub-directory, then WordPress should fall back to the default template loading rules. How can I achieve that?

Theme Customizer : how to create multiple-level panel

Is there a way to create deep-level sub Panel in Theme Customizer(like roots of plants) ? My theme that I have been developing seem to be more complicated. I think that if we can create deep-level sub Panel, our Customizer Page won’t look messy, our user will customize our theme easier and we will be able to make much more complicated WordPress theme easier. Images below describe what my idea is…

Is it ok to use a function to output the text domain name in a wordpress theme

I am working on a theme and I want to make it available for translating. I have not been including a text domain on translated text because I don’t know what the text domain is going to be yet. I figured, until I can come up with a name for my theme I should just use a function to output my text domain name instead of hard coding it on translated text.