You can do create a start form from workflow settings.

For a site workflow?  Can a site workflow be started manually rather than on a schedule?

Yes. Go to site contents, and on the top right you will see site workflows.

Is it possible to set a workflow variable from an InfoPath form? We don’t have Nintex forms.

I am not sure if you can use info path form as the start form for nintex workflows. With out of the box, info path form for start workflow is not available.

Hi Bright Light,

The workflow variable is on the start form.  But I can't bind the workflow variable to a lookup field in a list with a secondary data connection.  It gives me an error that I'm trying to bind it to a repeating table.  Why is a lookup considered a repeating table when it's just a drop down?

Do you have a repeating section on the infopath form?

It is a drop-down that uses a field in another list to populate it.  It's a lookup.  Really confused about it.