What do you expect Imageprint to use for printing as it can not interpret Lightroom catalog edit instructions? Lightroom has to send a rendered file to Imageprint which the Edit In command has chosen or you have chosen to be a Tiff. The edit In should have an option NOT to save the tiff back in Lightroom so your catalog does not get messed up. It will be up to you to delete the tiff from your OS.
If there is a setting to avoid saving the tiff back in Lightroom, I cannot find it documented anywhere.
I understand that the external "editor" needs to have a tiff file to edit or in this case print, but each time I open the original .NEF file or even a tiff file to edit in the external editor, and additional copy is made in lightroom with another '-edit989' or whatever the next sequential number is, is also saved in the catalog. Thus you can have something like _A0009876-edit 734 - edit 735.tiff etc. accumulating.
There is no need to save these TIFFs. but I'll be darned if I can figure out how to avoid this issue.
Same also happens with SilverEFEX, IntensifyPro, etc. I can't find anyone else that has noticed this behavior so I am stumped. Any further ideas.
If you are doing work using Photoshop then you will have to have a TIF image in the end. Photoshop, by itself, without Camera Raw, cannot edit raw image data and cannot save raw images. By the time the image has been opened in Photoshop it is no longer raw, and it's necessary to save the results as a TIF or PSD file. That choice is specified in the external editing settings in your Lightroom preferences. There is no way to Photoshop is capable of saving a raw image. It simply cannot be done.
If you are starting with a TIF image from Lightroom you should be given the choice to edit the original or edit a copy including the Lightroom adjustments. If you are not being provided with that choice then you need to reset your warnings.
The case of SilverEFX, etc is different as the results are wanted to be saved. For your ImagePrint not so. Why don't you export TIFFs to a folder and print from there rather than through the plug in?? Then you can just delete the files/folder on the OS easily.