Yes, I know that and on another site where I am testing different themes and Layouts plugin, I do have different Layouts created. See screenshots
When I use the Bootstrap 3 theme I can assign them to certain pages, but when using another theme, like Genesis Sandbox or Bootstrap Genesis theme which are both Genesis childthemes, that include Bootstrap, I only can assign a Layout to all pages, not to one specific. And when I create a new page, I can choose a template (see screenshot), but when I publish or update after choosing a Layout template, it is removed and it doesn't show on the frontend.
You can find both Genesis and the two childthemes here: hidden link
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Here is what I did, and I think I miss certain steps, but I have no clue which ones....:
I also tried to combine both the codes in one file, but that made no difference.
I also tried to use the code Luo provided into the functions.php file (without the <?php), but it broke.