A generic struct to show previews in various states. A combination of https://www.avanderlee.com/swiftui/previews-different-states/ and https://www.swiftjectivec.com/xcode-preview-snips/

UIElementPreview.swift

struct UIElementPreview<Value: View>: View {
    
    enum Format {
        case device, sizeThatFits, darkMode, rightToLeft, localizations, contentSizes, contentSizesMinMax
    }
    
    var formats: [Format]

    /// Filter out "base" to prevent a duplicate preview.
    private let localizations = Bundle.main.localizations.map(Locale.init).filter { $0.identifier != "base" }

    private let viewToPreview: Value

    init(_ viewToPreview: Value, formats: [Format] = [.device, .sizeThatFits, .darkMode, .rightToLeft, .contentSizes, .contentSizesMinMax]) {
        self.formats = formats
        self.viewToPreview = viewToPreview
    }

    var body: some View {
        Group {
            if formats.contains(.device) {
                self.viewToPreview
                    .previewLayout(.device)
                    .padding()
                    .previewDisplayName("Default")
            }

            if formats.contains(.sizeThatFits) {
                self.viewToPreview
                    .previewLayout(.sizeThatFits)
                    .padding()
                    .previewDisplayName("Default")
            }

            if formats.contains(.darkMode) {
                self.viewToPreview
                    .previewLayout(.sizeThatFits)
                    .padding()
                    .background(Color(.systemBackground))
                    .environment(\.colorScheme, .dark)
                    .previewDisplayName("Dark Mode")
            }

            if formats.contains(.rightToLeft) {
                self.viewToPreview
                    .previewLayout(.sizeThatFits)
                    .padding()
                    .environment(\.layoutDirection, .rightToLeft)
                    .previewDisplayName("Right to Left")
            }

            if formats.contains(.localizations) {
                ForEach(localizations, id: \.identifier) { locale in
                    self.viewToPreview
                        .previewLayout(.sizeThatFits)
                        .padding()
                        .environment(\.locale, locale)
                        .previewDisplayName(Locale.current.localizedString(forIdentifier: locale.identifier))
                }
            }

            if formats.contains(.contentSizes) {
                ForEach(ContentSizeCategory.allCases, id: \.self) { contentSize in
                    self.viewToPreview
                        .previewLayout(.sizeThatFits)
                        .padding()
                        .environment(\.sizeCategory, contentSize)
                        .previewDisplayName("\(contentSize)")
                }
            }

            
            if formats.contains(.contentSizesMinMax) {
                self.viewToPreview
                    .previewLayout(.sizeThatFits)
                    .padding()
                    .environment(\.sizeCategory, ContentSizeCategory.allCases.first!)
                    .previewDisplayName("\(ContentSizeCategory.allCases.first!)")
                self.viewToPreview
                    .previewLayout(.sizeThatFits)
                    .padding()
                    .environment(\.sizeCategory, ContentSizeCategory.allCases.last!)
                    .previewDisplayName("\(ContentSizeCategory.allCases.last!)")
            }
        }
    }
}

struct UIElementPreview_Previews: PreviewProvider {

    static var previews: some View {
        UIElementPreview(Text("Hello, world!"))
    }
}