You are most certainly not safe doing this.
Why do you want to keep the seed online in the first place? In practice you should not need to access the seed basically ever. If you need it near you for convenience, buy a Keep Metal and keep it in your desk drawer.
Putting your seed in a digital form exposes you to risks of malware attacks or being hacked. You can mitigate those risks by being careful, for as long as you can manage to be careful. But you could eliminate the risk completely by keeping the seed out of computers.
(even if you use an encryption program, you still need to decrypt the seed at some point, which opens it up to an attack.)
Not to mention, having the seed easily accessible also makes it easier for you to fall prey to a phishing attack.
(you went to the trouble of setting up a 24 word seed, presumably for the theoretical increase in security, now you’re about to undo it all by putting the seed in a digital device? come on.)
3 missing words out of a seed can be brute-forced in less than a day on current hardware. 4 will take longer but it’s doable and likely still worth it for potential thieves.
Any sort of scheme that requires you to remember weird details is bad as a backup; in a year from now, you won’t remember what you need to do to recover the seed.
Your home-grown “encryption scheme” is likely much easier to break than doing it by brute force.
If you want a factor apart from the seed, use a passphrase wallet, where even if someone has the seed, they still can’t access your fund without also knowing the passphrase.
But, more importantly, don’t let people have the seed in the first place.