Function add_menu

fn add_menu(
    ui: &mut Ui,
    base: Id,
    at: (f32, f32),
    target: Option<u64>,
    assets: &[(u64, String)],
    acts: &mut Vec<Act>,
    needs_undo: &mut bool,
)

“Add node”: every EffectKind under its category(), then the non-effect nodes and the project’s assets (an Asset node needs a real id, so it is picked here instead of on the node box). With target set it is the Replace menu instead: the same catalogue, swapped into an existing node.