So, I used to play the piano, and I understand that between bass and treble clef, you get most of the keys on the piano, and using octave notes can get you the rest. But pipe organs have a lot more keys…the Wanamaker Grand Court Organ has no less than 6 manuals (keyboards). There are 28,541 pipes. Countless stop plugs. The foot keyboard. Etc. How do you write the notation for that? Are there separate clef symbols for the other keyboards? Unique notation?
There is no separate clef for each keyboard. The keyboard to be used is indicated in text written throughout the score.
The usual indica are Gt., Sw., Ch.,Echo, Solo,Antiphonal. These are the names of the most common manual divisions of a large pipe organ. The 1st three stand for Great, Sell, and Choir.
The difference between them is that each will have different voices available to them (of course they can usually be inter-coupled). Each has 61 keys, unlike the 88 of a piano. THe pedal board has 32 notes. You use different keyboards, and the pedals, to bring out different sounds.
Contrary to other assertions, it's not always a "melody" in the right hand, or on the higher keyboard. It's often the other way around!