It's pretty clear what it's used for.
PartyMenuActionText is used for two things:
1) Storing what kind of action we're going to do (<$10)
2) Storing the text for some kind of healing stuff I'm not entirely sure (>=$f0)
In the former case, if GetPartyMenuTilemapPointers is ran, it will be
used to pick a sequence of actions that should be done, specified in the
table, and it'll print the corresponding string using the
PartyMenuStrings table. The items in the sequence of actions that should
be done are in WritePartyMenuTilemap.
Strangely enough, one possible value is left completely unused:
PARTYMENUACTION_GIVE_MON_FEMALE. It works in the exact same way as it's
male counterpart, and as such I don't believe it was used in the
japanese version either, since it doesn't matter which gender your 'mon
is when you put 'em in the daycare.
This function is called from a few different places in the mobile code,
including from one special that is only executed when the
BattleTowerRoomMenu special returns with a non-zero code.
Since that special causes a blue "error" screen to appear, that looks
the exact same as the one you'd get when trying to connect from the
mobile trade corner/battle colosseum in a Pokémon Center's top floor,
and this function contains a bunch of japanese strings in a jumptable, I
think it's reasonable to assume it should be called
"DisplayMobileError".
