HI turra, welcome on the forum!
First of all, you could use the Photoshop script to export your files, this way it would do all the placing and sorting in skin placeholders for you.
Regarding the parts that share the same name, if you need to manually add a second skin, this video could help:
Another option if you just need to place these new skins, you could use the photoshop script anyway and export the new skins, then import them as a new skeleton and manually sort them inside the right slots, this would only have the advantage of having a precise placing, but it should be your last option.