"Please follow the implementation guide/user guide for PegaMarketing available over PDN."
Why would you need to toggle between applications. If you create a Sales app, you'll have Access Groups that can be assigned to operators. There is your control. When you create Marketing App, you'll have new Access Groups. If you have users that cross the groups - simply add both access groups to that operator and pick one as default. That user will be able to use "Switch App" to toggle.