Thanks again, it's really appreciated.
I have done the changes and its like I'm almost there, once I paste the API I get the following:
[14:03:43.668] TinyPNG[Script Filter] Queuing argument ''
[14:03:43.725] TinyPNG[Script Filter] Script with argv '(null)' finished
[14:03:43.727] TinyPNG[Script Filter] {"items": [{"title": "Set API key to ...", "subtitle": "Set API key to ...", "valid": false}, {"title": "Get a new API key", "subtitle": "Open https://tinypng.com/developers to get a new API key", "arg": "WEBSITE", "valid": true}]}
[14:03:45.479] TinyPNG[Script Filter] Queuing argument 'GF4qGlzLMPr0fnV1mF9hDfxq9GH8f9rZ'
[14:03:45.535] TinyPNG[Script Filter] Script with argv '(null)' finished
[14:03:45.538] TinyPNG[Script Filter] {"items": [{"title": "Set API key to \"GF4qGlzLMPr0fnV1mF9hDfxq9GH8f9rZ\"", "subtitle": "Set API key to \"GF4qGlzLMPr0fnV1mF9hDfxq9GH8f9rZ\"", "arg": "GF4qGlzLMPr0fnV1mF9hDfxq9GH8f9rZ", "valid": true}]}
[14:03:46.638] TinyPNG[Script Filter] Processing complete
[14:03:46.640] TinyPNG[Script Filter] Passing output 'GF4qGlzLMPr0fnV1mF9hDfxq9GH8f9rZ' to Conditional
[14:03:46.641] TinyPNG[Conditional] Processing complete
[14:03:46.641] TinyPNG[Conditional] Passing output 'GF4qGlzLMPr0fnV1mF9hDfxq9GH8f9rZ' to Run Script
[14:03:46.642] TinyPNG[Conditional] Passing output 'GF4qGlzLMPr0fnV1mF9hDfxq9GH8f9rZ' to Post Notification
[14:03:46.652] ERROR: TinyPNG[Run Script] /bin/bash: : command not found
[14:03:46.654] TinyPNG[Run Script] Processing complete
[14:03:46.655] TinyPNG[Run Script] Passing output '' to Conditional
[14:03:46.655] TinyPNG[Conditional] Processing complete
[14:03:46.656] TinyPNG[Conditional] Passing output '' to Run Script
[14:03:46.656] TinyPNG[Conditional] Passing output '' to Post Notification
So it's like the API has not been accepted.