For the initial planning of a mission, you don´t need to be connected to the drone. You will just need the controller.

1. Fig. 1: Choose "Flight route"
2. Fig. 2: Flight route menu
   1. Here you will see all the routes you created before
   2. You can add new missions by clicking the plus in the top right corner
3. Fig. 3: Choose "Create a route"

1. Camera setup
2. Drone setup

For reference here also an official video by DJI: How To Start A Mapping Mission And Create 2D Maps- Episode 9