Implemented the NewTaskButtonModifier view modifier in the app target.

App/Sources/View Modifiers/NewTaskButtonModifier.swift

@@ -0,0 +1,98 @@
+import SwiftUI
+
+/// A view modifier that adds a floating action button for creating new tasks.
+///
+/// This modifier overlays a glass-effect button in the bottom-trailing corner of the view.
+/// The button can be conditionally shown or hidden with smooth animations.
+struct NewTaskButtonModifier: ViewModifier {
+
+    // MARK: Properties
+
+    /// Whether the floating button should be displayed.
+    let showButton: Bool
+
+    /// The action to perform when the button is tapped.
+    let action: () -> Void
+
+    // MARK: Functions
+
+    /// Applies the floating action button to the content view.
+    ///
+    /// When `showButton` is true, overlays a blue glass-effect button with a plus icon
+    /// in the bottom-trailing corner. The button animates in/out with opacity and scale transitions,
+    /// and includes a spring animation when pressed.
+    ///
+    /// - Parameter content: The view to which the button will be added.
+    /// - Returns: The modified view with the floating button overlay.
+    func body(content: Content) -> some View {
+        ZStack(alignment: .bottomTrailing) {
+            content
+
+            if showButton {
+                Button(action: action) {
+                    Image(systemName: "plus")
+                        .frame(width: 48, height: 48)
+                        .foregroundStyle(.white)
+                }
+                .glassEffect(.regular.tint(.blue.opacity(0.8)).interactive())
+                .padding(.trailing, 20)
+            }
+        }
+        .animation(
+            .spring(response: 0.4, dampingFraction: 0.8),
+            value: showButton
+        )
+    }
+
+}
+
+// MARK: - View Extension
+
+extension View {
+
+    /// Adds a floating action button for creating new tasks.
+    ///
+    /// This convenience method applies the ``NewTaskButtonModifier`` to show a glass-effect
+    /// button in the bottom-trailing corner of the view.
+    ///
+    /// - Parameters:
+    ///   - show: Whether the floating button should be displayed.
+    ///   - action: The action to perform when the button is tapped.
+    /// - Returns: The modified view with the floating button overlay.
+    func newTaskButton(
+        show: Bool,
+        action: @escaping () -> Void
+    ) -> some View {
+        modifier(
+            NewTaskButtonModifier(
+                showButton: show,
+                action: action
+            )
+        )
+    }
+
+}
+// MARK: - Previews
+
+#Preview("New Task Button") {
+    @Previewable
+    @State
+    var showButton = true
+
+    VStack {
+        Spacer()
+        Toggle(
+            "Show Button",
+            isOn: $showButton
+        )
+        Spacer()
+    }
+    .padding(.horizontal)
+    .frame(
+        maxWidth: .infinity,
+        maxHeight: .infinity
+    )
+    .newTaskButton(show: showButton) {
+        // On action closure.
+    }
+}