Function move/resize of titlebar

I just answered on your other thread about the exact same request:

I am not sure if the forums here have a policy on duplicated threads from the same author in a very short-period of time (I am new around here).

But my experience, in other forums, is that such behavior ends up leading to fewer people willing to help you.

Best of luck on your task.

By the way, the right-click works on the menu-bar as it uses a Qt standard component under the hood.

There is no KDE specific hidden code. You can choose to implement your application based on a UI toolkit (Qt, GTK, etc…) that already provides the features you need, or, as I suggested on the other thread, you can as Godot to expose such feature to their scripting language.

If you believe the toolkit you are using has enough features to implement this, I believe you will find more solutions on their own support resources (forums, etc.)

There is no KDE specific, nor hidden feature, to help you achieve such feature.