As for what attachment is visible, I could reproduce what you are experiencing. So as a workaround one can simply place the layer they want to be active at the bottom of the list for now. I've opened an issue here to see if this may be fixed:
https://github.com/EsotericSoftware/spine-editor/issues/600
TheWorst schriebAs for skins: why would i want to use skins instead of folders, when it's just those slots being problematic? eyelash_r and eyelash_l slots work just fine, despite featuring multiple attachments.
As you have greatly different hairstyles in the same slot that seem to be meant for skins, skins seem the logical option, and there's the very convenient [skin] tag that creates both a folder and skin with skin placeholders and everything necessary automatically. Of course you are free to also create them manually in Spine, but this would simply be less time-consuming.
Skins - Spine User Guide
If you intend to use this skeleton for different characters, I highly suggest you look at how skins can help you simplify this. If you are just goign to animate a change from one hairstyle to another, then I agree skins are not needed, but you'll need to duplicate animations if you want to have a walk animation with a hairstyle, and then another, you'll be forced to duplicate the walk and key the other attachments, which would be not needed with skins.
TheWorst schriebAs for the "keys deletion" I'm gonna send you a spine file with a key for the "eyelash_pain_l" attachment setting it as visible on frame 0 of the "tripping" animation. The key will be deleted as soon as you import the PTS .json file via "import into existing skeleton/replace" and select the chibi.json.
As you are choosing to replace the data already present in your skeleton with the new one you are importing, you are choosing to delete this information. This will also delete any mesh information you may have created to replace the art with the information in the json. As that json only contains the information generated by the Photoshop to Spine script, the keys get deleted.
If you want to preserve your work in Spine simply choose ignore, or delete the parts you don't want to replace right before launching the script in photoshop to avoid overwriting them on import.
Import - Spine User Guide: Import into an existing skeleton
