No need for registry edits. While the Microsoft version of Flight Simulator (as opposed to the Steam version) is a pain to modify, it can be done:
Download the "stick" and "throttle" files linked here: https://www.reddit.com/r/MicrosoftFlightSim/comments/ic90xr/x55_success/g21pouh/?utm_source=reddit&utm_medium=web2x&context=3
Extract them to a folder, if downloaded as a zip file.
Connect Joystick and Throttle to your computer.
WINDOWS KEY + R
%localappdata%\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\SystemAppData\wgs\0009000000195F8C_00000000000000000000000069F80140
Jot down the first five characters of each folder name:
<C4FEA> (Note: Anything surrounded by <> is an example only, your generated file/folder names will be distinct.)
<C6D89>
<DA9B0>
You will use these to identify which folders existed before you make new ones, later. Do NOT close this File Explorer window.
Start Flight Simulator
Options
Controls
Click Saitek Pro Flight X-55 Rhino Stick
Click Preset Manager (bottom of screen)
Click +
Name it anything -> OK
ALT-TAB back to File Explorer
Jot down the first five characters of the new folder. This is your Stick folder.
<EAE43>
ALT-TAB back to Flight Simulator
Click Saitek Pro Flight X-55 Rhino Throttle
Click Preset Manager (bottom of screen)
Click +
Name it anything -> OK
ALT-TAB back to File Explorer
Jot down the first five characters of the new folder. This your Throttle folder.
<56F89>
ALT-TAB back to Flight Simulator
Exit Flight Simulator:
Welcome
Exit to Desktop
Yes
Open the Stick folder
Copy the long filename: <A8C17F977B1A4357B4DC511C39D6E542>
Delete the file with the long filename.
Rename the stick file to the above filename.
Move/Copy the new file to the folder from which you just deleted the old file
Open the Throttle folder
Copy the long filename: <39609CD93C314458A241E56267510527>
Delete the file with the long filename.
Rename the throttle file to the above filename.
Move/Copy the new file to the folder from which you just deleted the old file
Close File Explorer. Start Flight Simulator.
Options
Controls
You'll see the profile loaded in for both the Stick and Throttle: Screenshots