I also would like an option to disable detaching tabs. I often detach by mistake.
If the window is maximized and I use the mouse to click on the start menu, I usually go all the way to the bottom left corner of the screen and click. If I do this, Terminals will detach the window.
Another common situation is if I have windows open and use the task bar at the bottom of the screen. If I move my mouse all the way to the bottom and click, it detaches the screen.
Clicking on any of the left, right, or bottom edge of the window will cause the window to become detached. I have to train myself to not go all the way to the corner or bottom edge of the window and that's very difficult to do.
I'd appreciate it if this feature can be disabled.