Each item you add to your Alexa To-Do List will also be appended to a "todo.txt" file in the root of your Dropbox. You shouldn't need to use the actual Alexa list at all!
This Trigger fires every time you add an item to your To Do List.
This Action will append to a text file as determined by the file name and folder path you specify. Once a file’s size reaches 2MB a new file will be created.
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Amazon Alexa and Dropbox