Why are some dynamic derivatives not included in DATCOM file?
A plane is subject to 5 forces: Thrust, Lift, Drag, Weight/gravity (and side force). In addition, there are 3 moments: Rolling, Yawing and Pitching moment. With these 7 vectors you are able to represent how a plane behaves in the air. The problem of simulations is how to compute these 7 vectors for a complex shape like is an aicraft in different flight conditions. To obviate these issues, engineers came up with 'coefficient of ..' which is indicated by C_letter.

To make estimation of these coefficients more accurate, engineers decided to compute the partial derivative of each coefficient due to 'something'. However, some of these derivatives have a small influence on the coefficient such that only for high fidelity simulations they are used (for example in Level-D simulators). Moreover, depending on the type of aircraft, some derivatives may be important or not: if a plane has no slats then there is no lift coefficient due to slat failures.

DATCOM was developed in the seventies and computing power has improved a lot since then, therefore some coefficients are not included (yawing moment due to angle of attack).

A nice reference to understand why coefficients are used if the book Boeing - Jet Transport Performance Methods.