I like planning a, and yet I'm still caught off guard sometimes
Recently I developed a process using obsidian, although it isn't a 'writing app.'
Basically I plan out the ideas and topics. Plan out the basic story structure using 7 plot points and/or the 3 act structure. Then I start writing a brief summary of everything I want to happen in the story, as if I'm telling it to someone. Noting down the characters feelings and whats going through their minds. I'll then rewrite that going into more details.
I'll make an outline using this summary, separating everything into scenes. Then I'll write the scenes, already in the character's or narrator's voice.
When I have that first draft of the scenes, I'll start organizing them into chapters. Each chapter can contain 1-3 scenes, depending on what they tell, and their theme. And that's it.
A lot of writing and rewriting.