No, it seems that this is not possible at the moment. Others have talked about the same problem here and here.
Someone there has written that he could change/add tags within the things menu of habmin. But others reported that this hasn’t solved the initial problem. At least you can try it this way…
So at the moment it seems that you have to manually create the items you want to use in HomeKit and create an items file for this. In this file you can then add your tags (like described in the docs).