When you add a folder or a file present in an external drive to hide into Hide Folders and then hide it, the application stores information about the item location in a fìle stored inside your user's Application Support folder. It's like making an alias to that file.
If you use another computer and use Hide Folders, it reads the information stored in Application Support folder of that computer which of course knows nothing about what's stored on the Application Support folder of the other computer.
So to hide and show items of an external drive in two different computers, follow these steps:
- Mount the external drive in computer A.
- In Hide Folders, choose the files you want to hide.
- Mount the external drive in computer B.
- In Hide Folders, hide the files.
Now both computers know where that file are and each copy of Hide Folders should be able to hide or show it when that drive is mounted.
In order to recover a hidden folder or file, just follow this guide: How to recover not listed hidden items.