Hi …,
Welcome.
For Charts, the Export function goes to the last save folder used.
If you save to …\X-Plane 12\Output\FMS plans this should be remembered.
For SimBrief, the Download function goes to the last save folder used.
If you save to …\X-Plane 12\Output\FMS plans this should be remembered.
You also have the SimBrief Downloader which I highly recommend you install. You can easily set up the download folder to be …\X-Plane 12\Output\FMS plans, and in Change Settings, set to Always export new flight automatically. Then when you press Generate Flight in SimBrief, the flight plan will be automatically placed in your desired folder.
You can also set to automatically download different formats to the many different required folders, all when you press Generate Flight .
Cheers
Ian