You can pre-select a Conga Email Template by copying the template's record ID to the clipboard and pasting it into your Composer button's URL following the &CongaEmailTemplateId=id parameter. An abbreviated parameter name, &CETID=id, may be used instead.

You may only specify one Conga Email Template Id per Composer button / link.

If you specify a Conga Email Template Id, but not a file template id (&TemplateId), Composer will display the list of "Conga Email Templates" (with the selected email template) by default.