Using JEFIT you are able to download and store multiple routines within your account to use with the application and website.
You are indeed able to record and perform multiple routines at once while using the application.
What you can do is begin performing your workout routine using the "Start A Workout" (Android) / "Routines" (iPhone/iOS) page and begin a workout session, then when you are ready to use your 2nd workout routine.
You will click back and enter your "Routine Manager" page within the application via either the "Find A Routine" button (Android) or "Download More/Routine Manager" (iPhone/iOS).
From there you will be able to view all of the routines that you have within your account and stored in your profile. Then click on the routine you want to perform, select an exercise day from that routine and perform the exercises that you want from that routine.
You can then switch between this page/routine and the main default routine while still tracking your workout session until your workout is complete.
After you will then end the workout from the default routine section to get your workout session feedback from what you have just performed.