Hey Flow9881, thanks for the question! While we do not currently support multiple decks per Actor, there is a definitely a way to do this:
1. Create two Actors which will serve as the player. One is the Combat character, one is the Negotiation character.
2. Before a Combat Encounter, remove the Negotiation character from the party and add the Combat character. Before a Negotiation encounter, remove the Combat character from the party and add the Negotiation character. This ensures that the correct deck is being used in each case.
3. If you have level and stat progression in your game, create a Common Event that you call which sets the levels and stats of both characters whenever a switch happens. Call this Common Event before you swap the characters before each encounter.
4. When you are adding new Cards, you can choose which character learns it by using the script call:
$gameActors.actor(X).learnSkill(Y)
where X is the ID of the Actor and Y is the card added to their Deck. We don't want a case where the Combat character is getting Negotiation cards or vice versa.
There is a downside with this method currently in that when your player looks at their Deck, they will only see the deck of either the Combat or the Negotiation character. You can have an Event that the player can interact with which switches the characters to alleviate this issue.
We will be adding support for Card Types soon with the v.1.4.0 of the plugin. That should allow you to specify what are Combat cards and what are Negotiation cards so that when looking at the Deck screen, the player is clear on which Deck they have for a given situation. Once we have support for switching Classes in (by v.1.5.0), this will become as easy as switching the class of a single character.
Hope this method helps. Let us know if you have any other questions or would like to troubleshoot this until we get it working :)