When planning fiction I'm considering planning possibilities rather than specifics. Normally a "plan" would mean writing down things that are supposed to happen, and a particular order they are supposed to happen in. Instead of planning what is "supposed to" happen, it seems more interesting to leave things vague. I can sketch possibilities and figure out the details when I write the relevant scene. That might work differently from trying to plan more of the story.
I've been unconsciously doing this with a story I'm working on lately and it seems to work better than planning to the letter. I have a disorganized mass of ideas like: "I want to have a scene set in a museum about a character who wants to touch these bones but they are behind glass." Or: "Maybe there's a scene where this character is dressed differently because they want to impress this other character." Or: "Here's a different character or subplot I could write in." Or: "Here's a line of dialog that I like." I'm keeping things loose. The sense of possibility hasn't dissipated yet, so maybe it helps.