Allow Re-Docking of Detached Secondary Windows

Allow users to re-dock detached secondary windows into the main application window

Problem Statement

Currently, when a secondary window is detached from the main application, there is no dedicated way to dock it back. The only available option is to close the detached window using the X button.

This behavior is unintuitive because users generally expect the X button to close the window completely rather than return it to the main application. As a result, users may hesitate to close the window or be unsure how to restore the original layout.

User Need

As a user, I want to re-dock a detached secondary window into the main application window without closing it, so that I can easily restore my preferred workspace.

Proposed Solutions

One or both of the following interaction patterns should be supported:

Option 1: Re-dock Button Provide a dedicated "Dock" or "Return to Main Window" button in the title bar or toolbar of the detached window. Clicking the button docks the window back into its original location in the main application. Use the new icon of https://github.com/eclipse-theia/theia/issues/17789

Option 2: Drag & Drop Docking

Allow users to drag the detached window back onto the main application. Display visual docking indicators while dragging. Dropping the window onto a valid docking area re-attaches it to the main window.

Expected Benefits

• Improves discoverability and usability.
• Aligns with user expectations from modern IDEs and desktop applications.
• Reduces confusion caused by using the X button for a purpose other than closing.
• Enables a faster and more intuitive workflow when switching between docked and detached layouts.