Juxtaposing successive levels from parent-child relational data

Hi! I am trying to reconstruct hierarchical relationships from exported data from a database which contains lots of rows. Some rows do not contain enough of the keys necessary to establish a parent-child relationship, but there are always at least one row and often several which do contain the necessary keys to establish a link between two levels in the hierarchy. There hierarchy consists of three levels, but all three levels may not yet have branched out completely at any given time.

The example in the attached workbook should make the task clearer. I have tried building up the formulas by using a lot of different array functions from all over the Interwebs, but haven't been able to arrive at something that works all the way and in a neat way.

I'd appreciate if anyone is able to crack the code for this.

Best regards,
Marbleking