Solution 1:

On Win10 there exist two versions: Bedrock/Win10 edition (just called Minecraft nowadays), and Java. On XboxOne there are two versions: Console edition (deprecated, can no longer buy), and Bedrock edition (and bedrock is a free download if you had console). On Nintendo Switch there are two versions, console edition and bedrock (and bedrock is a free download if you had console).

If you want to play multiplayer with another device, the general rule is the devices must have the same edition.

You have Bedrock on win10 (it's the one that comes from the Microsoft Windows store, not mojang.com). You don't say what you have on XBoxOne, but if it's not bedrock, then download bedrock for free. If you want the Switch to get in too, get Bedrock for it (the only version purchasable today). On each device (win10/xbox/switch), log in to a different XboxLive account. For each account, friend the other two accounts. Then on one device, start a world. On the other devices, that world should appear in the friends tab.

Android and iOS phones can also join, as they run Bedrock edition.

Solution 2:

Cross play is ONLY for bedrock (Win 10 ver. through the store, mobile, xBox, and switch) Usually you can set up a lan server by going to your world options, multiplayer, then there should be an option to broadcast to LAN. Another option is that you need to sign in to xBox live (on ALL devices you want to use) with different accounts. Friend each account together and in world options turn on multiplayer game, allow friends of friends.

To view steps, go to this link (New link)

Solution 3:

You should be able to create a LAN -Locan Area Network- or if that doesn't work, thanks to the Better Toghter Update, you can now crossplay. On the Switch for example -I happen to own one as well- when you press "Play", you just navigate over to the "Friends" tab by pressing 'R' -top right bumper-, type in the person's username you want to add, and they will be added to the friends list. It will also show you when they are online as well. Hope thie helped you, and my Minecraft name is Spencer incase you would like to play together.