At a high level of abstraction, being on hold because of a dependency indicates a problem in a business process. Fixing the problem or mitigating its effects seems like a responsible thing to do. On the other hand, if there is some pressing personal business, down time created by the inefficiency might be a good time to schedule the time away from the office.
My random advice from the internet: look around and see what your co-workers are doing. Talk to your boss. Keep in mind the type of person you want to be and to become. Consider the possibility that a job without enough interesting and important work to keep you engaged is more likely to hinder your career over the long term than advance your skills.
Good luck.