You could use the waypoint function in DJI Go 4 app and save the waypoint you want. The difference being that you'd have to fly the mp to the location you want and save a waypoint manually. I'm not as familiar with the go 4 app version of waypoint, so I can't say if it has time setting to tell it how long to stay in that position or not. There is a setting I know about in there that will allow you to say what to do when the waypoint mission is complete, and I'd think you'd want the "hover" instead of rth option. I've seen some really awesome time lapse done using the tripod mode too, so you may want to explore that, but these weren't multiple day missions like you're talking about. (I have the same idea, so this has just turned into a personal challenge to beat you to it)
