Chrome extension to trigger file upload without user input

I have listed this as a javascript project as I suspect that javascript -and probably an extension for Google Chrome browser - is going to be the primary method to solve this although I am open to other solutions.

The situation is thus -

We have a file upload field on a website - actually Amazon Custom data upload screen:

... input name="file" id="asset-upload-tester1" class="a-button-input amz-custom-upload-file preview-image-change-upload-file" type="file" value="Change Image" aria-labelledby="a-autoid-21-announce" ...

We need to upload a large quantity of images but it is going to be time consuming to do this manually.

I want to PROGRAMMATICALLY, via Chrome extension or otherwise, point this field towards a pre-specified local file, and submit.

I SUSPECT that utitilising one of the Chrome extension APIs MAY make this achievable - maybe fileBrowserHandler:

https://developer.chrome.com/extensions/fileBrowserHandler

If this is NOT possible, any alternative method to automate the "click upload" -> "paste file URL" -> "click OK process" is acceptable.

Please do not submit generic proposals, but provide evidence you have actually read the specification.