Hi @Anonymous ,
Could you please share a bit more about your Launch formula?
Do you want to navigate to specific screen in your Second app from your First App?
Based on the needs that you mentioned, I think the parameter value within the Launch function could achieve your needs. Within your Launch function, you could specify a Parameter value (called "ScreenName"), then provide a proper value (target screen name in your second app) for it.
I have made a test ob my side, please take a try with the following workaround:

Set the OnSelect property of the "Launch" button to following:
Launch("https://apps.powerapps.com/play/31232661-a6b6-494d-b01f-029ec943420f", "ScreenName", "Screen1")
Note: You should replace the "Screen1" with actual Screen Name (string value) in your second canvas app
Then within your second canvas app, set the OnStart property of App to following:
Set(ScreenNameValue, Param("ScreenName")); // Use Param function to receive parameter value passed from your first canvas app
Switch(
ScreenNameValue,
"Screen1", Navigate(Screen1),
"Screen2", Navigate(Screen2),
"Screen3", Navigate(Screen3),
...
...
)
Please consider take a try with above solution, then check if the issue is solved.
Best regards,