After installation the addon will be located at: -> 3D Viewport -> N-Panel -> K-Tools.

Any Idea, suggestion or critics please reach me out! You also can try my other addons!

About the Addon:

With this addon, you will be able to sync all your viewports at once without using the 'Lock Camera to View' Technic. This is useful for keeping both Rendered View and Clay View in sync when checking your scene or locking the view rotation to avoid unwanted misclicks. The addon allows the user to choose what features will be synchronized also, what view will b ein sync with the Master.

NOTES: Master Viewport: Mean the Viewport that will ‘rule’ all the selected ones.

Features:

• View Synchronization Panel

• Single match: Match all selected viewports based on the Master Viewport with a single click.

• Real-time Sync: it is a Boolean button, once enabled it will sync all the selected view in real-time based on the ‘Refresh rate’

• Master ID: It defines the Viewport that will command all the desired ones.

• Refresh Rate: The time (in seconds) what the synchronization will occur; lower values, faster the synchronization will be.

• Adjust View Distance: It is a multiplier that allows the user control how much ‘zoom’ will have on the controlled Views, this is useful when the aspect ratio of the controlled view is different from the Master View.

• Clip Start | End: Default Blender view clipping - "Clip Start/End adjusts the minimum and maximum distance range to limit the visible range to the area between two planes that are orthogonal to the viewing direction of the viewport camera. Objects outside this range will not be shown." - Blender Manual*

• Focal Length: Blender's default option - "Control the focal length of the 3D Viewport camera in millimeters, unlike a rendering camera." Blender Manual*

• Local View: This is an upgraded operator that works as the default one from Blender, the difference is that it will also set the Selected Objects in Local View mode in all Views at once.

• Local View + Lights: Works as the previous Operator but also adds into the Local View the Visible Lights in Scene, now you will not be in the dark if you isolate some model in the rendered preview mode.

• Available 3D Views: It is the list of the available viewports in Blender, if you have more windows, two lists will be drawn side by side.

• Identify 3D View: It shows a Pop-up telling you what if the viewport what you are in, if you add this operator into your quick menu, it will show the viewport ID what you called the operator.

• Update View List: Redraw the Available 3D View list.

Sync Options (Subpanel):

These options control what will be updated.

• Distance: Updates camera distance when true.
• Location: Updates camera location when true.
• Rotation: Updates camera rotation when true.
• Camera Zoom: Updates camera zoom when true.
• Camera Offset: Updates camera offset when true.
• Perspective: Updates view perspective when true.
• Clip Start: Updates view clipping start when true.
• Clip End: Updates view clipping end when true.
• Focal Length: Updates focal length when true.

Lock Rotation Panel

• Available 3D View: Shows the viewports that are available to be locked.

• Identify 3D View: the exactly same operator from the Sync Panel.

• Update View List: Redraw the Available 3D View list.

Special Gizmos: Show in the Locked Viewport the following buttons: Toggle Solid Shading; Toggle Material Shading; Toggle Render Preview; Shading Menu Popover; Set Camera View; Move the View and Zoom in/out.

• Set Clean View: It will ‘clean’ the view that is Locked, the header, default gizmos and overlays will be disabled, they appear again when you click the button once more.

Known Issues: When 'Real-time Sync' is Enabled, the Move, Rotate, and Scale gizmos might not work properly at times if the Refresh Rate is too low e.g. 0.1 seconds. This can be solved by increasing the refresh time, or, setting the Controlled Viewport in a different window.
These functions will work correctly if used via the G, R, and S keys.