How do it get sub categories in A to Z order of a particular category in each block and label them alphabetically. Note that A, B, C, etc. are just label.
For example:
A
- A sub category 1
- A sub category 2
- A sub category 3
B
- B sub category 1
- B sub category 2
- B sub category 3
C
- C sub category 1
- C sub category 2
- C sub category 3