@luckywp:
Wouldn’t it be responsible to give the 100,000+ users the answer to James’ question (and the other users who asked)? There are many users who have installed your plugin on a large number of WordPress instances, set it up and customized the output. It would be really nice to know if we all need to look for a replacement in the medium term.
We all know that plugin development maintenance and support is a lot of work. Especially when there is no payment for it, it can be difficult in the long run. But it would be really nice to know what you plan to do in the future. At the moment the plugin is still working wonderfully, but that can change quickly, as we also all know very well.
So I also ask: Do you just leave it as it is as long as it works and then rework it, or do you want to give up the plugin?
And I would also like to take this opportunity to thank you for this great, easy-to-use and customizable table of contents plugin and your great work for over 5 years!