Using a barbell and a power rack, you can do deadlift isometrics that can directly increase your deadlifting ability. But you must understand your weak points to know which isometrics will work best.
For most people, the sticking point in the deadlift is right below or above the knees. If that’s the case, then isometrics in that range can be very useful.
(Other people have trouble right off the floor; if that is the case, extended deadlifts can be a better option, even extended deadlift isometrics.)