cant add whole branch

That is all that SmartCopy adds at one time ... the profiles immediately connected to the 'focus' profile.

You then move to an adjacent profile (depending on which direction you are building) and add *those* adjacent profile. Repeat.

It is highly recommended that the Geni tree view be checked every 2nd generation to check for both consistency AND to check for duplicates with existing Geni profiles.

It is quite normal for a potential Geni match to quickly show up once the parents & siblings have been added.

Max , 10 years ago users could import whole branches, indeed whole trees, into Geni in a single step. It resulted in massive amounts of duplication and confusion which still can be glimpsed in the tree all these years later.
Smart Copy's process is intentionally limited in this way to minimize the likelihood of duplicating existing profiles.