So you saved a default preset & now you're sick of loading it all the time. You want to get back to what the default was out of the box because Bitwig knows best. Unfortunately, the process right now kind of a pain, but it is still possible:

1. Load the device that needs to be reset.
2. Change/tweak a parameter.
3. Use the 'Save as Default Preset' function to overwrite your current default preset
4. Open your Bitwig Studio settings folder (this is a hidden folder, so you will need to adjust your file browser settings accordingly!).
5. In the settings folder, search * to perform a search for all folder items.
6. Sort the search results by change date to see the device you changed most recently first.
7. Delete the file. If you want to confirm this is the right device before deleting the file, just drag the file into the Bitwig device panel area.

Once you load the device again, you should now be back to the default state of the device before you saved over it!