Provides a simple subscript focused API for easily binding DisclosureGroup or Section expansions including persistence across app launches.

Named Expansions.swift

import SwiftUI

struct NamedExpansions: RawRepresentable {
    @Observable
    final class Wrapper {
        var sections: Set<String>
        init(sections: Set<String> = []) {
            self.sections = sections
        }
    }

    @Bindable
    var wrapper: Wrapper = .init()

    var rawValue: String {
        wrapper.sections.joined(separator: "|")
    }

    init(rawValue: String = "") {
        wrapper = .init(sections: Set(rawValue.components(separatedBy: "|")))
    }

    private func bind(to section: String) -> Binding<Bool> {
        .init(
            get: { !wrapper.sections.contains(section) },
            set: { expanded in
                if !expanded {
                    wrapper.sections.insert(section)
                } else {
                    wrapper.sections.remove(section)
                }
            }
        )
    }

    subscript(_ name: String) -> Binding<Bool> {
        bind(to: name)
    }
}

Example:

struct Sidebar: View {
    @SceneStorage("expansions") private var expansions: NamedExpansions = .init()

    var body: some View {
        List {
            Section("Home", isExpanded: expansions["home"]) {
                // ...
            }
        }
    }
}