I believe the once the passband width is set, you should be able to move it around without it changing. The controls work as expected in the "high / low" mode.
On phone it collapses the width when it gets to the carrier frequency and does not cross it. You would think it would just stop. I have never had a use for that filter mode in phone though.
It seems to me that center is a method for tuning modes with a center carrier like CW and AM.
I would agree that it should not change the width when you hit center but don't understand why you would want to use this mode on SSB anyway.
a way to make the RX filter controls default to LOW/HIGH instead of
I find that I mostly use the LOW/HIGH feature of the bandwidth controls most of the time and would like that to be the default mode instead of having to press and hold the button every time I use the radio to switch from SHIFT/WIDTH to LOW/HIGH.