Okay, so I managed to pull off the impossible task. Here's a guide as detailed as I can go.: (Windows Only, will look for other options for macOS and Linux :{ )
Warning: GBATemp, the developers of TegraRcmGUI, and myself (Hipeopeo) are not responsible for bricked Switches. Proceed at your own risk.
Note: Your microSD will not need any files to be put on it, but it will still need to be in the Switch to be modified.
1. Download the latest
TegraRcmGUI, and either install it, for extract it.
2. Open TegraRcmGUI, go to settings, and click "Install Driver", and go through with the installer that pops up.
3. In TegraRcmGUI, go to tools (The buttons should be greyed out. If they're not, skip step 4). Make sure "Memloader v3 / UMS Tool" is set to "MMC - SD Card" in the option thing after "Mount".
Warning: Do not select any other option. Those are unsafe for inexperienced users.
4. Make sure your Switch is plugged in to your computer, and boot into RCM.
5. The buttons should become available (ignore this if they already were). Click on the button with the USB drive on it, next to "Memloader v3 / UMS Tool". Your Switch should flash a bit, maybe some text, then stay on a glowing screen. You should now be able to access your Switch's microSD from File Explorer.
Note: To end the connection, hold the power button on your Switch until it turns off.