Highlight Mode while using the HDR Panel

I recently watched a Resolve training video regarding the HDR panel in the Color Tab. In this video, it showed how the Highlight Mode can be used to show the ‘mask’ for a selected HDR zone.

In the top-left of each zone wheel in the HDR panel you can click-and-hold the icon, and as long as the mouse is down, the Viewer will show the areas of the frame that are within that zone. When the mouse is released, the Viewer shows the frame as normal. In the training video, if the Viewer Highlight Mode is selected, the same ‘mask’ is shown as long as the Highlight Mode is selected. I can see where this might be very handy while grading using the HDR zone wheels, as it is clear exactly what is being impacted in the clip (much like using Highlight Mode with a qualifier).

I’m using Resolve 18.6.6, and with a single HDR zone active, turning on Highlight Mode does nothing in the Viewer. I don’t know if this feature is no longer supported, or whether I’m doing something wrong. Does anyone else use this feature in 18.6.6? I saw in the release notes for 18.6.x releases that Highlight Mode had ‘addressed some issues when using the HDR panel’, but the notes were not clear on exactly what changed. I can really see where the Highlight Mode would be very handy for an HDR zone. Anyone know how to get this to work?

I only know it works as long as you hold the mouse.
Can you link the video here were it shows working without holding the mouse?

It is in an online class I have been taking. I have emailed the author to get the exact instruction, but the online video shows the mask becoming visible when highlight mode is selected when the HDR panel is active (I’ve watched the video several times). I hope to get clarification soon, and will post what I find. I suspect that something has changed in a recent update.

...Anyone know how to get this to work?

You have to make an adjustment to a wheel to 'activate' it.
Elsewise, Resolve doesn't know which wheel to show the highlight for.
Select highlight mode, adjust the Spectral wheel, it now shows the spectral area affected.

That solved my issue. Thanks!