The PC will not crash when trying to open up another instance after closing the initial one if you:
1. Close the original instance of the game
2. Open the Launcher
3. Go to Task Manager and terminate the Launcher task.
4. Reopen the Launcher and start a new instance
Another method to prevent a crash is to:
1. Close the original instance of the game
2. Uninstall the MInecraft Launcher from the "Apps and Programs" section of the Settings app.
3. Go to the Xbox app and redownload the Minecraft Launcher.
4. Reopen the Launcher and start a new instance
Can confirm in 1.18 Release Candidate 4.