Answering my own question, I came up with a way to do this but based on the Dropbox OAuth Guide I strongly believe that this is not following best practice on the Dropbox side so do not use these instructions unless you really know what you are doing.
Anyway, after logging in to Dropbox I went to the App creation page and create a new app with these settings:
Then at the next page, grant the newly created app
files.metadata.write permissions and click Submit to accept these changes:
Back on the Settings tab, select the Access token expiration (for my demo I set it to “No expiration” even though this is going to go away soon because the Python filesystem plugin doesn’t support renewing short lived tokens even though long-lived tokens are deprecated). Finally generate a token and copy this to the correct area of your preferences (User menu → Preferences → Manage information)
The error message generated when this setting is correct (
Problem listing file source path FileSourcePath(file_source=, path='/')) is definitely not user friendly but hopefully this reply provides some guidance on how to configure this plugin. No doubt details will change in future to accommodate the shift to short lived tokens.