How can I translate a custom liquid code element in the customizer (for translate & adapt app)?

[Michel]

The question is: How can I translate a custom liquid code element in the customizer (for translate & adapt app)?

I used the strings that are recommended like "{{ '+ For better sleep add a flat sheet' | t }}" but it just shows an error like here on the image:

 

[saim007]

@Michel Please provide url where you want to implement this so i can understand the issue.