Relative new at extracting report from iModel.
I was looking at creating report similar to the attach picture.
Using a simple QTO button, we select elements from the Model structure, then we choose which attributes to expose in the report, the order to display them.
Choose flat representation or as the Model Structure
Set the title of the report ( 1 or two lines)
Tweak the text by column bold, italic, color etc...
Export as excel or PDF
etc...
See also as a reference openplant Wiki, where it show how to edit the BOM report. Same idea under an iModel design review