Cover author and pubdate in footer

[Yeriel]

Hello,
I am unsure if i am right.
I want to create a cover with Calibre. I found the settings and the text tab were I can enter the template language. The title works well. The subtitle more or less.

My first question: I need a interlace in the subtitle. e.g.

Subtitle (interlace)
Part 1:.....

My second question:
The template text fr author is given. I want to add the pubdate without override the authors.

Does anyone knows the answers or the right items to program this?

Thank you very much.