I’ve honestly never used qTranslate. Multilingual websites in general are not something that I have much real-world experience with, but I do provide pretty good support for WPML in my themes if you ever go that route: http://wpml.themeblvd.com
I just searched around a little about how to use the plugin. And I just downloaded and looked in to to see how they filter the content. They’ve essentially got one filter there that you could possibly apply to the content/columns element of the Layout Builder.
To give you a little bit of compatibility, you could try possibly adding this to your Child theme’s functions.php. In theory, from looking at their source code, this should make it so you can do the same things in the content of a post/page as in some elements of the Layout Builder.
add_filter( 'themeblvd_the_content', 'qtrans_useCurrentLanguageIfNotFoundShowAvailable', 0 );
So for example, I’m assuming in the “Content” element or the “Columns” element you could use this syntax they provide something like this:
english textgerman text"
Note: For the “themeblvd_the_content” filter to be applied, you need to check the box in the Layout Builder “Apply WordPress automatic formatting” on those elements you’re editing.