The system I work with for my game has vars for every state, so like if the player jumps while running it might look like this:
Idle_(Default)
Walk_(Fast)
Jump_(Long)
Land_(Moving)
As apposed to when the player jumps while idle:
Idle_(Default)
Walk_(Default)
Jump_(Static)
Land_(Static)
I also use bools that manage the player states to keep condition comparisons as small and readable as possible.
I've also found that it's important to be able to turn off parts of the animation system like walking, idle, and jumping to make adding new mechanics a lot easier.