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This feature uses wowhead page from any NPC to collect required datas to display it wow model viewerin WowModelViewer, see this example below :
I wan to display "Skeer the bloodseeker", here is the result in wowmodelviewer WowModelViewer :
Unfortunatelly, there is no answser. Let's click on "Import from URL", you will see this dialog:
You just need an a wowhead URL to fill it, so let's go on your browser, and search for your wanted NPC (skeer the bloodseeker in our case) :
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You now just have to click "Display", and thtthat's it, Skeer the Bloodseeker is displayed on your viewer 
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