Hi, you can use Find and Replace to change the attachment path on many attachments at the same time.
Please see Tree - Spine User Guide: Find and Replace for more information.
Here's an example where I replace boy/ with images/boy/ in the path for all region and mesh attachments in the current skin
And here's an example where I use ^ under Find to match the start of my path and then replace it with images/boy/
So to get what you're after, first move your pngs into the folders where you want them, then use Find and Replace to update the path of your attachments.
I hope this helps!
