Add ability to upload saved settings

Please add ability to upload a settings file. We can download a JSON or whatever, which is helpful. When there's a new release, it's hard to determine exactly the settings used with a previous build. Being able to upload the a saved JSON or other settings file would be very useful.

The issue names no files, tests, or entry points. Start by locating the existing settings download behavior and how settings are applied, then define the accepted saved-file format and validation; done means a previously downloaded settings file can be uploaded and restored reliably.

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