It sounds like you need to use random mode in drills (‘Rnd’ button in the top right corner of each drill). Currently, there’s a limit to what you can do with it, because it’s ‘all or nothing’ in terms randomness of shot choice. However, there is is a software update due out, hopefully this week, that should significantly improve the random mode in drills.
At the moment if you make a drill with 4 shots; short BH, short FH, long BH & long FH, and stick it in random mode, the robot will pick completely randomly between all 4 shots. So you can get a complete mix of short and long balls as well as left and right. The mix seems to be proper RNG and sometimes you can get a nice even mix and occasionally you’ll get a lot of one shot, etc. It’s good but unpredictable and tough if you have to cover the extremes of movement, in/out & left/right.
What I’m hoping for from this update is that you’ll be able to have the same 4 shots but make the robot alternate between 1 short (FH or BH), then one long (FH or BH). This will be very useful.
There is another random mode (actually there’s 2, AutoRND & ProRND) for single shots which gives a bit (or a lot) of randomness of placement to a single shot. It very useful but like you say, it doesn’t seem to stay if you then put that shot in a drill. Hopefully this will get fixed with the update too.
At the moment to do what you’re trying you have to put multiple shots in a drill and then stick the drill itself on random mode.
Hope this helps.