Hi Mouda,
As doc mentioned, there is an exsiting flag(two oprion field) called marketingonly in lead entity, if we qualify a lead, a workflow will executed to create a contact record from this lead, and by default this field is set to false.
You can find this flag in contact form > Details tab > Marketing section:

You can even add this flag to any view of your contact to get a clear overall view:

And when you create a contact directly in marketing module, just set this field to Yes.
What's more, there is another helpful field called Originating Lead, same in Details > MARKETING, this field will only be populated when the contact was qualified from lead (actually there is still a third identity/flag field called Lead Source, by default is not visible on form, we could add it on contact form manually)

Then you can filtered out two type contacts and might not need a lead based segment.
Finally, a workflow would be helpful for you to set interested/not interested leads, run them with your own business requirement.
Regards,
Clofly.