Hi Dan!
Thanks for getting in touch with us!
First, please let me note that we are fairly limited in how much support we can give for custom development questions like that.
That said, we always like helping out and at least point users into the right direction as much possible.
The filter bar collapsing is the default behavior for narrower windows because the mobile styles are being applied so that it looks good on mobile devices.
You could add some custom code to tweak the default behavior so that the filters always show when resizing back.
I hope that helps.
Best,
Victor