[WIP] Add toggle for numbers and TOC button to Headerbar

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

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This section details on the original issue you should resolve

<issue_title>Toggle the numbers, add TOC button to Headerbar</issue_title>
<issue_description>While the Plugin works fine most of the time, it would be great to have a means to disable showing the numbers, and just have the titles in the TOC. Can you point me please where in the code I could achieve that?

It would also be great to have the TOC toggable via Headerbar, I guess I could write a Plugin just for that, maybe you could also point me to the right direction.

Thanks for all your Work!</issue_description>

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