How to create custom variable (%%title%%) for meta field in wordpress for yoast seo plugin

I want to create %%title%% variables for meta field which I want to use in yoast seo settings.

Please guide me how can I do this

You can target a custom meta field by using %%cf_<custom-field-name>%% in your SEO Title field.

Here's a reference of all the available variables on Yoast:

Yoast SEO: Titles & Metas template variables

Here's an example of what it should look like: