If you have been using SimBrief to create routes to import into MSFS, you're probably aware that, when you attempt to start at the gate, MSFS will completely change your route. Let's hope that Asobo fixes it soon.
In the meantime, here is an explanation of one way you can workaround this.
After you download your route using the Simbrief Downloader, open explorer and navigate to your \AppData\Roaming\Microsoft Flight Simulator folder.
Right click on your route (.PLN file) and choose Open with. Choose Notepad.
The route will open in Notepad. Scroll down until you see <DepartureName>AIRPORT</DepartureName>
Copy and Paste <DeparturePosition>GATE X X PARKING NONE</DeparturePosition> just below it. (For example, departure from Gate B4 would be <DeparturePosition>GATE B 4 PARKING NONE</DeparturePosition>).
Change the first X to the Gate Letter and the second X to the Gate Number.
Scroll down until you see the first <ATCWaypoint id="AIRPORT"> (located after </AppVersion>)
Delete the entire line <RunwayNumberFP>XX</RunwayNumberFP>
Save the file as a .PLN file by choosing Save As, After the File Name type .PLN, in the drop down choose Save As Type: All Files, click Save, then choose to overwrite the old file.
Load the route into MSFS, and it should display the correct gate and the route you created without any changed waypoints.
Another method I've read about is to download and use Little Navmap. Load your route into Little Navmap, change your departure to the gate, save, and import it into MSFS. I personally have not tried this method.