What type of footnotes do you need to attach?
Generally, the information you enter from the K-1(s) you receive are dispersed throughout your personal income tax return; the K-1, itself, does not get filed with your return - you retain it for your records.
No, you cannot add any addendum if you intend on electronically filing. If you file by mail, you can include additional documents, but this is NOT recommended. What do you need to explain? If the IRS wants further information, they will request it. @mrKlein
Turbo Tax does not support Self charged interest so I wanted to point out what I did to handle it for purposes of full disclosure.
Self charged interest ??? You charged yourself for a loan to yourself ? Please explain further.