You need some kind of SSO for that. You can open App 1 > login to SSO > Open App 2 > SSO instantly redirects you because you're still logged in.
Have a look at this Webinar (within minutes 9-13.5) to get an idea what you can try to implement for your needs using DeepLink marketplace module.
https://ww2.mendix.com/cw-integrating-microservices?utm_campaign=esw035&utm_content=DevSite