the Edit Bedtime function can only be accessed if Siri Suggests it - as of 21st of October 2018. This might change in the future, however.
I have seen that Shortcuts 2.1 Beta 2 has introduced actions such as:
- Get Current Weather
- Get Weather Forecast
- Create Alarm
- Toggle Alarm
- Start Timer
So we can rest assured that there are more actions coming into Shortcuts, and they're a mere AppStore update away. Here's hoping that Shortcuts 2.1 will come out around mid-November or before start of December, would be great.
There's no talk of entering Edit BedTime though, as that's a really useful feature to have on an iPhone, ever since Siri Suggested it, I've incorporated it into my Beddybyes shortcut that sets my phone up for going to bed, and the last action is to start up Edit Bedtime, I set that and then just lock the phone and zzz away.