GSX doesn't interface or use or connects in any way with FSUIPC, it's completely self-contained. Also, you posted this in the MSFS section, but you call it GSX, so it's not completely clear if you are using MSFS or FSX/P3D, because there's a big difference between the two:
- In FSX/P3D, GSX does set the airplane in Slew mode during QuickEdit, as it does with every of its editors. There's no way to prevent or change this, because GSX keys in FSX/P3D are only working in Slew. The only solution is to use pre-made Pushback Slots or a pre-saved QuickEdit.
- In MSFS, GSX Pro DOES NOT set the airplane in Slew mode, because the editor works in a very different way, using the Showcase Drone camera, because Slew mode in MSFS has a forced camera view that doesn't work for editing. What's happening during Quick Edit instead, is that GSX freezes the aircraft momentarily, but it's not slew mode, it's just setting some variables to temporarily disable the flight model to keep the plane in place during editing.