How Do Support Slots Work (Battle)

[Seisachtheia]

So I've tried rotating through some of the different characters you can put in the party support slot...and some of them just don't seem to work? Specifically, any character that's supposed to have an effect in battle doesn't seem to (I have Kurtz in there currently because I thought...oh free meal before combat...except...nope. No indication that anything is happening).

Are these support characters just bugged, does the game just not tell you what they are doing?

[VertVentus]

Supports you choose at the start of a round

• Kassius (Once, 100+ All Damage)
  
• Allaby (Infinite BGM Change)
  
• Hogan (Flee)
  
• Stadler (Three, Party SPD Debuff)
  
• Rody (One, Party SPD Buff)

Supports with an RNG chance to activate at the start of a battle

• Perrielle
  
• Euma
  
• Cabana
  
• Galladur
  
• Kurtz
  
• Code L (frequent?)
  
• Douglas (frequent?)

Rohan's 20% HP post-battle recovery works passively with no animation.