Hi ebirdman,
The on-line SDK tool which you can select your own related board or chip, and generate the directly project.
Do you mean the installed SDK in the MCUXpresso:

Do you mean remove the related SDK?
If yes, you just need to delete it by right click and uninstall it.
You can let me know your detailed question, eg, which SDK, IDE you are using, which detail boards/devices you want to remove.
https://mcuxpresso.nxp.com/
This area can generate the detail boards, after you select the related board, there will don't have other boards.
Wish it helps you!
Best Regards,
Kerry