Export and Paste Over Original

To recover disk space by exporting and pasting over the original file:

Select and export the presets that you want to keep into a temporary folder, saving the file with the same name as the original file.
Navigate to the folder where you saved the exported preset file, select the file, and cut or copy it.

Notice the file size on the example above is just over 13 MB.
Navigate to the Bryce Presets folder then to the folder where the original file is located.
Paste the new file into the folder, confirming on any replace messages.

In the example, the User.obp file is being replaced. Notice the file size on the current version is over 17 MB. By exporting out the objects in the User category and copying it over the old version, 4 MB of disk space have been recovered. This may not seem like a lot, but a MB here and a MB there can start adding up very quickly.