Hi @patty789 ,
Do you want the user to navigate to specific screen when they click the app web url within the email body?
Based on the needs that you mentioned, I think the If function and User function could achieve your needs. I have made a test on my side, please consider take a try with the following workaround:
Set the OnStart property of the App to following:
If(
User().Email = "User1@email.com",
Navigate(Screen1),
User().Email = "User2@email.com",
Navigate(Screen2),
User().Email = "User3@email.com",
Navigate(Screen3),
...
)
In addition, you could also consider store the related users for corresponding screen (in your app) using individual Excel table data source, e.g. Screen1Table, Screen2Table, Screen3Table, ... etc. The data structure of ScreenTable may like below:

Then set the OnStart property of App to following:
If(
User().Email in Screen1Table.Email,
Navigate(Screen1),
User().Email in Screen2Table.Email,
Navigate(Screen2),
User().Email in Screen3Table.Email,
Navigate(Screen3),
...
)
or
If(
User().DisplayName in Screen1Table.UserName,
Navigate(Screen1),
User().DisplayName in Screen2Table.UserName,
Navigate(Screen2),
User().DisplayName in Screen3Table.UserName,
Navigate(Screen3),
...
)
Please consider take a try with above solution, then check if the issue is solved.
Best regards,