If you want to send/receive projects on the Digitakt - you can do it with SysEx dumps and your favorite SysEx librarian.
If you’d like something that will do the transfers and give you more visibility and control over projects use elk-herd: Elk-herd 3.0 beta: Project Import at last! (it’s free and no installation needed).
As been stated, you can’t import M:S projects into DT… but if I ever get around to adding M:S support in elk-herd, then interchange between the two would be a cool feature.