I have no experience with New Blue, but you are probably correct that they are FxPlug based code plugins.
They make plugins for a variety of editors, the last supported seems to be Final Cut Pro.
I tend to view these types of plugins as "sanctioned viruses" — Apple allows them, but they can be doing things you might not be aware of. One thing they do track is whether or not a product has been purchased so it can limit your use of plugins as "Demos".
Historically, FxPlug added templates tend to *break* when FCPX is updated as well as when the OS is updated. These include plugins from FxFactory, PFS, MotionVFX, etc.
The Transitions you have that are blank probably *broke* a year or so ago. Therefore, you *might* have to upgrade the software to get a working uninstaller.
I have no idea how you ended up with this product, but I seriously doubt it was bundled with FCPX and Motion. New Blue isn't even listed in Apple's Final Cut Pro Ecosystem page.
I've searched around for removing these effects and can find very little. There is basically only this:
https://newbluefx.zendesk.com/hc/en-us/articles/206317045-How-do-I-uninstall-a-NewBlue-product-
NewBlue Uninstallers may be a folder - if so, you'll find the uninstaller for each product you might have installed inside the folder. Once you get them all removed, you'll need to get rid of the NewBlue App Manager as well.
Apparently, you are likely to also have a User Account on NewBlueFX.com which you will need to deactivate (Sign Out).
Whether or not all this will actually work to get rid of these effects once and for all... your guess is as good as mine.
Good luck.
