Preset Cameras erase all other cameras

I just bought a scene that comes with a series of preset cameras, but no way to load them all into the scene at once. I have to click on each one from the library to enter it into my scene.
I'd like to have more of these cameras in the scene at once, but even if I create my own cameras in the scene, every time I click on one of these preset cameras it deletes any and all cameras I've created. Only the one new camera and the original ( F, R, L, B, T and Perspective) views remain.
Is there a way to keep this from happening? Thanks!
Comments
Use the Ctrl/Cmd key when adding another camera with a preset. This will open the "Camera Preset Load Options" dialog. This will allow you to choose how new cameras are added to the scene. You can set the preferrred action for future use. Note that the ctrl/cmd key will open a Preload Options dialog for any asset type, not just Cameras.
@NorthOf45 - Thanks. That's good to know info.
In order to aply the preferred options you need to hold down shift while double-clicking the preset - which can be tricky as you may add the one you just double-clicked to the selected presets and then applying all, doubling up any earlier presets.
That works great! Thanks!!