I think it is a good idea in theory also, there I just that voice that says "well now that key is out of my possession" and it scares me a bit.
I think I might need to look up to see if there is a known pattern to these keys that it could be easily figured out what it is even if it is just on a sheet with no context. Particularly 1Password which I think is a pattern if I remember correctly.
Or, just apply some simple, easy to remember permutation to the key that no one would be likely to guess - eg rot13 the key, or add 1 to every character, move the first 14 characters of the key to the end of the key, etc.
Probably that the key has features that allows 1Password (and potentially anyone) to recognize that its a 1Password key. E.g. Fixed size, patterns of spaces or dashes, specific digits, embedded error correction, etc.
Similar to how a lot of package companies have a certain pattern, length, whatever for their tracking numbers. If there was a somewhat reliable way to say "This is a 1Password key" or "This is an iCloud key" it makes it means even without context it could be an issue.
I think I might need to look up to see if there is a known pattern to these keys that it could be easily figured out what it is even if it is just on a sheet with no context. Particularly 1Password which I think is a pattern if I remember correctly.