If my private dock was dredged recently, is there a reason to still be a part of the umbrella permitting process?

It would be advisable to review your current permits to determine when they expire. If there are still three or more years on the permit, then, assuming the USACE initiates the federal channel dredging within three years, you will not need a new permit through the Umbrella Permitting process. Those permits can be used to participate in the umbrella dredging episode to be performed in conjunction with the USACE dredging. If your individual permits expire in less than three years and you choose to not participate in the Umbrella Permitting process, then you may have an expired permit and unable to dredge at the time of the USACE dredge episode.