Is it 'safe' to store hashed values of my mnemonic seed phrase on my computer? I am setting up my hardware wallet, and have written down my mnemonic seed phrase physically, but also want a way of accessing it from my computer.

If I add all the seed words together, and hash it by a specific combination of the existing words, would it be safe to store on a computer?
The outputs of hash functions cannot be reversed. So what is the point of storing the hash of your seed? Perhaps you mean an encrypted version of your seed? That would be storing the ciphertext of your seed. You could do that but just so you know there's already an encrypted version of your seed stored in your wallet file. Otherwise there would be no way for the wallet to sign spending transactions.