For setting up this behavior, I set up an attacking combo system and ability system. The combo system tracks how many attacks you can do, how far into your combo you are, and checks what your last 2 attacks were.

The ability system has a list of objects with data that can change how the player's behavior might be affected. Some of these alter the combo count in some way, though like Kingdom Hearts, a lot of these are attacks with animations tied to them.

Within these abilities, a lot more information about the attack is defined. In here, the animation is linked up directly to the Unity animator component by selecting an enumerator, and other stats can be defined further on how that attack animation behaves.

Many of them are tied to the animation itself, ala Animation Notifies, tracking where in the animations the attack can be canceled out of, how long they last (for the combo counter), and how gravity is affected

Also within each of these abilities hold custom root curves for altering the player's root motion quickly in-engine. Root motion works well as it does, though with an approach like this, if any changes need to be made, the animation can stay consistent while the root motion can be altered with ease, without needing to swap between programs.

With animations hooked up through abilities, depending on what players have equipped, they will have a different set of animations to play and cancel into. For this to work, each attack ability has a set of transitions for the animation to go to when the player continues their combo. These transitions check which ones are equipped, then which is higher on the list, but also have a priority number assigned to them in case one is deemed more important than the others.

As a final note, take a look at all the animation states that were used and implemented for this project! There was a lot of linking and transition rules, and keep in mind that some of these are also accessed through the abilities and find their way back home, as Unity (to my knowledge) has no direct equivalent to animation montages.