Start Form / Transaction not working

Hi Experts,

I created a custom workflow that is working fine in test mode.

The requirement is to start this workflow manually, then I'm trying to add a Start Form to it.

First I created a Workflow Container Element with Import attribute flagged:

Then I tried to reach the Start forms tab page in the version-dependent basic data, as described here: https://help.sap.com/saphelp_di471/helpdata/en/96/f32bb6d48011d195120000e82dec10/content.htm

Unfortunately, I don't have this tab:

I can find it only in Version-Indipendent options, but when I try to use it, I receive this warning, and I cannot proceed:

"The container does not contain a suitable element for the form data"

Please, help me to find a solution for that.

Since the screenshots have a very bad quality, I attach also a document with the same: Workflow Issue

Thanks in advance and best regards,

Ermanno