Custom Placeholders for untranslatable variables

I have some variables that do not appear as placeholders in the editor. How can I set the placeholders and prevent them to be translated?

In the Translation checks area, there is an option to customize placeholders per file format. You can set the delimiters using custom placeholders, and all variables that appear between those delimiters would appear in the editor as placeholders. You can set warnings or error to make sure translators are preserving them in the translation box.
You can refer to best practices here: