Yeah, you can change the url to "...appurl?screenID=4&widgetid=5" for example. There is probably already a question mark in your app URL so you'd just need to append "?variable=value&variable2=value2".
Then in the app you can use the Params function to write "Set(variable1,Param("variable1"); Set(variable2,"variable2")". This checks the url for second term in "" and sets it to the variable name you specify.
A more useable example would be:
www.appurl.com?screenID=details&itemId=4
In the app.On Start:
Set(varItemId,Lookup(ItemsDataSource, ID = Param("itemId"));
Set(varFirstScreen, Param("screenID"))
In app.StartScreen:
Navigate(varFirstScreen)
If in doubt, I always find Shane Young (https://www.youtube.com/watch?v=7MxXmGOkeLQ) has some great videos
Hope that makes sense, but let me know if not
