A possible improvement to the friend list would be a way of sorting characters by elements used by the character, Sorting by specific tags/killers they have, What spellcard shot type they use and/or Sorting by Type strength/weakness.
As a whole if there was a way of sorting Characters by any of the above would make it much easier to select characters of certain types.
For example: when looking for a character that has certain types (Sun/Wood AOE Ofuda attacker for example) you'd have to scroll through all the characters you have until you found the character(s) that fits the types mentioned and trying to find specific character(s) for situations can take minutes and makes going up in Scarlet Devil Tower, Element EX and VS Characters a chore.
This is an issue for long time players more than newer players but I think implementing this would be a good change.