Is not under either Basic or Advance configuration > Image > Backlight Settings? Which browser are you using? Just in case, try using Internet Explorer with the camera plugin installed.
I was using Edge, the plugin didn't work with that and Firefox wouldn't log in at all. I was able to get the plugin to work with Internet Explorer but I still don't see anything about WDR. Thanks BTW.
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Oh, I think the option is not there because the camera has a 120dB True Wide Dynamic Range and there is no need for software WDR. At the same time, I'm no expert, so take it with a grain of salt.
Sorry, only just read this. It's because BLC and WDR can't be on at the same time, but you figured that out! Same on the Hikvisions for anyone else with the issue.