You can make it safe by using a secret key in conjunction with the keys. For example; all passwords as written but the third character must be # instead of what

You can make it safe by using a secret key in conjunction with the keys. For example; all passwords as written but the third character must be # instead of what's written. This renders the book useless if stolen or copied. If you keep the book in a locked draw and use some tell tails to ensure that you will know if it's been opened you have a strong chance of being able to know if you have been physically compromised. Any online key store is vulnerable in a number of ways, end to end security is hard. The biggest issue is that your provider might be placed under significant physical pressure relieved only when your account is compromised. And you will be unaware.