By default, you are limited to one Microsoft account per computer user account. This can make switching between accounts difficult. You can change this, though it requires a bit of advanced setup. To keep things clear, the following two terms are used:

• Microsoft Account- This is the account you use to log into the Microsoft Store and Minecraft.
• Computer user account- This is the computer account that you log into when you start up your computer.

To use multiple Microsoft accounts on one computer, you can create a different computer user account for each purchase of Minecraft you have. Note: Each Minecraft purchase will use a different Microsoft account login.

• Click the Start button in Windows, click Settings (cogwheel), go to Accounts, and then click Other Users.
• Click Add someone else to this PC and fill in their information. You can choose to create a user with a Microsoft account or make a local user without an account. 
• Do not use an exclamation mark or Minecraft will not run.
• Log in to the other Microsoft account associated with the Minecraft profile you want to use for this computer user account.
• Download Minecraft from the Microsoft Store.

For more information, please visit the Windows help site.