Custom variables in KMail snippets

Hello.

I am setting up my mail in Kontact/KMail and there is a nice plugin Quick text / Snippets included.

In kde documentation there is very little information - just how to add the snippets.

When composing a message, using the prepared snippet with custom variables, it is possible to make a custom variable to have a default value.
This makes me suppose that there might be an option to define a list of values to choose from and / or there must be at least a “place” to edit those values. And I can not find them.

This is so promising and I would really like to get some help on this.