There's a general roadmap. It's a piece of paper next to my laptop. No, you can't see it.
There are also very thorough design docs for every feature Sigil has currently and has had previously. There are also lots of design docs on features that are still on the drawing board, features that I've committed myself to implementing and on features that are "would be nice to have, but currently no plans to implement them". All of these docs are in various stacks of notebooks in my computer room.
No, you can't see these either.
Why all this "you can't see them"? Because I've discovered that the more I talk about certain features, the more people want them (and sooner), and the more I get annoyed with endless "when will it be done" questions.
I've talked about some general plans a few times and in a few places, but nothing is official and frankly, I'd much rather you, the userbase, didn't know. I constantly change my mind about what should go where and why and on what schedule. Some of these internal "course corrections" happen because I notice a higher demand for certain features. Sometimes it happens just because the next thing on my list is boring to work on and I frankly don't feel like spending my free time working on something boring right now. The boring stuff thus may get pushed back.
In any case, every course correction to work on certain other features delays the arrival of features that I originally scheduled. Since different people care about different features, this would inevitably lead to anger amongst the people who care more about the features that have been delayed. No matter what I work on, someone's going to get mad that I didn't work on their "biggest missing functionality of Sigil IMO".
So to avoid all this, the roadmap stays private.
When I start working on something, I
may tell you if I think it's wise. I usually don't.