Maybe I'm misunderstanding your question, but the significance of the outline being written on Eddie Kane's typewriter is that it provides very strong evidence to Franklin's claim that Kane murdered Alan Mallory and framed Franklin due to Alan plagiarizing him with Franklin's help. Eileen had said earlier: "Alan wouldn't plagiarize, he wouldn't have to". But with the outline having been typed on Kane's typewriter is hard to dispute Franklin's claim.
It's only when Eileen says: "It almost feels like Alan dictated this himself", that Columbo gets the idea that Franklin could have been paying the night messenger to give him Alan's manuscripts. Therefore, Franklin secretly knew what Alan was writing, and he could type a copy on Kane's typewriter.
Thanks for your answer, I am sorry maybe my English is not good enough. I understand the meaning of the plot and everything is fine about that. What I mean is that this outline is quite long - obviously a lot of pages written. I think it takes a long time to write something like that on the typewriter. Especially that Greenleaf wrote 2 copies - for himself and for Eddie's drawer. So that means that our dear Riley had to spend a lot of time in Eddie's apartment to write it. This is what I meant :)
I see what you mean. It's either a plot hole, or you can assume that Riley owned the typewriter and typed the manuscripts himself every night. Then, just before he planned to kill Kane, he gave the typewriter to him as a gift. That way Greenleaf only had to type the outline at Kane's house and would have the entire manuscript stored in his safe.
About the key: the locksmith would go to the office and either take the lock apart and work out how to grind a new key, or put in a blank key and put turning pressure on and the marks on the blank would show what needs to be ground away to make a new key.
The mystery to me is why Greenleaf would make it look like he was being framed and put himself into the situation, when all he had to do was make the false alibi, then nothing.
I think Greenleaf wanted to frame Eddie Kane. Columbo said to Riley: "somebody has a copy of that new key, and when I find that key, I have my murderer". So Greenleaf had a new key made and planted on Eddie Kane. The problem was, Columbo was setting him up from the beginning.