Nim access to OSX cut and paste buffer:

[treeform]

You could try GLFW:

`install staticglfw`

<https://nimdocs.com/treeform/staticglfw/staticglfw.html#getClipboardString%2CWindow>
 
<https://nimdocs.com/treeform/staticglfw/staticglfw.html#setClipboardString%2CWindow%2Ccstring>