${template.ext} in workflow

I need to generate file names in workflow so I’ve selected “Trough workflow” as Output management in Create output. How to set correct extension for this filename?
In Output preset I would use ${template.ext}, but what to use in workflow?

You will have to hardcode it in whatever means you use to rename your file.
If you could have both PDF and PS output file from the same process, then there are ways to condition on the beginning of it:
PDF file always start with %PDF- if you look at it with a text editor (line printer emulation).
PS file always start with %!PS-Adobe- if you look at it with a text editor (line printer emulation).
This way you can condition on this to choose you extension.