I am not sure if there is an option for choosing the order, but I do (kinda) know how the order is decided
It depends on the word/character. If you have a subclass that starts with an A and a subclass that starts with a B, then the A will be the top one.
If you have a subclass that starts with an a and a sublclass that starts with a B, then the B will be the top one. Not sure why but it's like that.
If you have Level 1 and Level 2, then the top one should be Level 1, unless your Level 1 starts with a small L, then it will be Level 2
Say you have Level Start and Level end, then Level End will be the top one as the E is earlier in the alphabet then the S. You can change this by making the e small.
I also tested this with a $ sign and that is earlier then the capital letter. Not sure which ones are earlier then the $
So the order is as following:
Signs such as a $ that work
Capital letters in an alphabetical order
Small letters in an alphabetical order
Level 2 is earlier then level 1 as level 1 has a small l whilst Level 2 has a capital L
If you want something such as Level Start and Level End then I recommend that you either make the E small or that you make it something like Level 1 Start and Level 2 End.
Also you can't do a space between the subclasses, you need to do something like a underscore (Level_1)