Each piece of clothing is equipped with its own armature. Normally we want to join all armatures which control both the character and all clothes. The Merge Rigs button merges all selected rigs to the active one. Since the main character rig is usually active after import, the quick way to do this is to press A-key twice (to deselect and select everything) and then press Merge Rigs.
We see in the outliner that the rigs that were parented to Ana have disappeared, and that the meshes are now directly children of the Ana rig.
When the rigs have been merged, we normally only have to merge or reparent the toes. Since Ana is wearing boots, there is no reason why we should want to pose the toes individually, so we press Merge Toes to let the big toe bone control all toes. For some reason the toe bone points in a weird direction, but this can be easily fixed in edit mode.
There is usually not necessary to use the other buttons in this section when the file is imported with Mesh Fitting set to Json file. They would have been necessary if we had used the deprecated Obj File or Dae File fitting options. See the documentation for version 1.1 for details.
