You could theoretically use the OS.execute() command to run application on Android by am start -n com.example.project/.ExampleActivity
but its not a good thing to do, because you would need to specify the package name and activity name which could be changed at any time and it would not work again... If you want to do it for "share" function, best thing you can do is write module with some android share library (like this one) and call it from GDscript that way...