Add-ons or Usercripts

Hello,

I’m fairly new to app development, so apologies if this is an obvious question.

I would like to know whether there is a way to add small, optional enhancements to K-9 Mail without forking the repository and maintaining a separate build (which would prevent regular Play Store updates).

Some of the features I’m hoping to add include:

  • Expanded search filters and criteria

  • An “unsubscribe” button in the message list or message options, which would:

    • Trigger the unsubscribe link automatically (if available)

    • Delete the current email

    • Auto-delete any future emails from the same sender

    • Optionally remove existing emails from that sender already in the inbox

  • Client-side rules for organizing folders

  • Automatic saving of contacts when replying to messages

Ideally, I’m looking for:

  • A method of applying customizations (e.g., userscripts, plugins, or similar mechanisms) that can be easily disabled or removed

  • An approach that preserves the ability to update through the Play Store

I am already a beta tester and have submitted feedback, but I realize some of these requests may run counter to the app’s lightweight design goals.

Does anyone have advice on how to achieve this sort of customization?

Thank you!