For you, it is naturally important to choose the direction of your future work. However, the two directions you have chosen are not two incompatible directions; they are, in fact, interchangeable, as long as you have the will to do so!
As of now, central air conditioning repair requires a higher level of skill, and the social value should be higher than refrigeration operation. But you yourself have emphasized your weak maintenance skills, which may be a hindrance to your further advancement ---- Why are you so unsure? You should know that you work as a refrigeration operator without much experience in servicing, and your servicing skills are naturally weak. But as you start from scratch, how do you know you can't improve your servicing skills soon?
As for refrigeration operation, I believe that the future is not forever to operate refrigeration! You have an electrician's license, a pressure vessel operator's license and so on and so forth, in a number of years can be developed to equipment management, this in the factory also gives you a good development.
So, the current advice is that if you are confident enough to believe that you can handle the challenges, then you should opt for central air conditioning repair. But if you are not willing to face the challenges, then continuing your refrigeration operation is also a good option. Make a choice after you become a little older and feel that you will be better off and also capable of developing!