[Simple Inqury] Adding an additional column in waypoint file?

#### Issue details

I am wondering:
1) How can I add an additional column in waypoint data? Essentially I want to add a mode within the waypoint to manage a specific state so that my Copter or Rover can change cameras (or something) based on the current waypoint. This is the simplest reason why I want to add another column, such that my Copter will execute a function after reaching a waypoint.
2) Where in the mission planner software I can add such changes, including to add this column of data in the exported WP file?

#### Version
Latest

#### Platform
[X] All
[ ] AntennaTracker
[ X ] Copter
[ ] Plane
[ X ] Rover
[ ] Sub

#### Airframe type
Copter Quad.

#### Hardware type
Pixhawk or PXFmini -- I can deal with the solution on the hardware level.

#### Logs
_Please provide a link to any relevant logs that show the issue_

The issue names Mission Planner, waypoint data, and exported WP files but no files, tests, or entry points. Start by locating the waypoint import/export and mission-handling areas, then determine how an additional waypoint field would be represented for Copter and Rover and how completion would be verified.

Written by the indexing model from the issue text.