Doubt about Mailto function in GS

Hello All,

I am not a PRO user yet and have a doubt about mailto function in GS.

Can we use variable in the following for substituting values on the fly in GS:
mailto:example@example.com?subject=THisIstheSubject&body=ThisIsTheBody

i.e var1= THisIstheSubject&body and var2= ThisIsTheBody

Also, when running the mailto function through a button(actor) click, Does it open the email app with written template or just sends the email with the initial button (actor) click itself in first go?

Thanks in advance.

Regards