I have created a custom Outlook form and added an action to open
another Outlook form (a standard Outlook form) directly from my custom
form. I set this up in the actions tab of the custom form.
When I use the form, the button to open this other form only appears
after I save information in the form and then re-open it. Why? Is
there a way to set it up so that the button appears whenever I launch
a blank form?

What I am trying to achieve here is to have Outlook automatically
include the information in the custom form as an attachment to the
form that I am launching from the custom form (which is an option that
I can set on the actions tab).

I would be interested in any possibility that allows me to
automatically attach the content of the form from which I am launching
the new form, but I am trying to avoid using VBA script.

To my knowledge, you will NOT be able to perform that task without VBA.