oh wow. I feel like I may be responsible for that feature. I damn near made that request specifically.
So I'm still working out the details and caveats, but the gist is this: You hit random or whatever and like the play order but want to rearrange like 2 of the songs. Select all and copy to play order, then unrandom so that you can adjust the playlist, and do what you want. The playlist order is now what you just had.
I kind of expected this to happen automatically if you tried to adjust songs to a new order while in random (or other fixed) view. Instead if you try to reorder a fixed view you just get denied. So this is the workaround.
Mea culpa. I requested this feature.

Maybe they're listening to me.
Oh, and the confusing part is probably that the command affects the entire playlist. It has nothing to do with what you have selected. To see your current play order, click on the number field to order.
There are a few things about that interface that should be cleaned up so that meaning is more obvious, but all of the playlist management functionality that I desire is now there.