Can you designate a Home Xbox without using the console?

Unfortunately no. You have to be signed into the console you want to designate in order to do so.

Hi there,

We appreciate you reaching out to us with this issue. You can only have one console marked as your Home designated Xbox to share games and Xbox Live. So, you can be logged into the console you're playing on without disturbing the Home console you designated.
The other two consoles would need to have another Xbox Live subscription attached to them. Thank you.

Hello Damoo76

he can play any disk copy on his console that you give him without any issues. digital games you have to put your account on his console then designate his console as your home Xbox. here's a link if you need more information about designating your home
Xbox.

https://beta.support.xbox.com/help/hardware-network/console/my-home-xbox

Hi witchywond

Designating a 'Home Console' is for when families who have a dedicated console for family use and a second console for another member to use at the same time. 'Game Sharing' as you have described it, is not what the service was designed for and could get your account suspended.

How your friend has it set-up (with sharing games and subscription with his brother) is fine and is how it's supposed to be used. If you then designate your Xbox as your friends 'Home Console' and your friend designated his Xbox as your 'Home Console' then this will make it work but it breaks the link with his bothers console and violates the terms of use.

More details on home consoles can be found here:

Designate a home Xbox | Xbox Support

Hope that helps.

The my home Xbox is designed to share games on a console of your choice. If you have used up your 5, then got another one, used that one on another console, then it will remove the home Xbox from the last console you designated as the home console. There
is nothing you can do to change it back, except wait until 365 days is over.