I keep accidentally moving the filter panel and have to reset it by right-clicking the header. Please add a lock option for it to always be attached.

I'm also a bit unhappy with the current situation. I will see if I can do something about locking the window. Would a checkbox in the PGF options panel be sufficient for you? I would rather not implement another button in the header bar, changing the UI is always a major effort.

As long as there is some way to lock it I'm happy.

Now possible with by setting "Dialog movable" to false in the options panel