Hi MikroTech ,
Thank you very much for your reply to this post.
The import features has not been added in yet. The free version will have it next year.
WP All Import was not tested as we want to bring out our own premium add-ons for ATUM. The Export PRO is already being worked on, however, we have still some time before its release (early 2019 we estimate).
ATUM is growing in popularity and there is now 4000+ users, maybe if you ask the WP All Import guys to support ATUM they will.
My team does not have the resources to support 3rd parties as we have tons of work for another 10 years.
Hope you understand.