Excuse me, it is the query boxes, not the search boxes, that already have the call.  Unlike the other boxes I initially tested, they do not have the traffic lights.  I believe that this, not movability, is the effect on mac of 'movableModal'.  I tested a messagebox and it also had no traffic lights.

What effect does the change have on Linux?

On my MacBook, IDLE preferences is too tall, so that the bottom buttons are not visible and the only way to reliably cancel is to click the red button on the title bar.  So remove the change for that at least until we have redesigned the dialog to be wide instead of tall.  There is also an IDLE issue questioning whether Preferences (and Search) should even be modal.

Currently, IDLE file open and save-as drop down from the center of title bar, have no traffic lights, and cannot be moved.  Open is the entire width of the screen and could only go up and down.  For Open, the underlying window is moved to the center.  For Safari, Save as is the same, so I question whether it should be changed.  Safari's Open is movable.  Neither window for either app currently has traffic lights.