One DEQ Weirdness figured out for good, I hope

I've figured out (again?) why the Behringer DEQ delay settings, on the I/O page 4, often have Left and Right lumped together and you can't switch channels by simply pressing the "Left/Right" button.  This is maddening because for the subwoofer, I need to put in different delay values for each channel.

If the button has both Left And Right highlighted, it needs to be held down for a few seconds then either Left or Right is selected, and the other becomes selectable with a tap.

To go back to delay settings in both channels, you hold down the button again (technically it is "Button A") for a few seconds, and then it reverts to Left And Right again.

It has nothing to do with the "Stereo-Link" (vs "Dual Mono") setting in the Utility manual, something that the DEQ manuals back to 2007 have emphasized.

Funny I thought I did this last night, after desperately trying other things, and then trying to remember what I had done before, but it didn't seem to help.

Then I tried it this morning, and voila it worked.  I got the idea after re-reading these ambiguous lines in the manual:

With the A key you can select the left or right stereo side. Independently of the Stereo LINK mode both sides can be processed separately. Keep the key pressed to edit both sides simultaneously.

"Keep the key pressed" sounds like you keep the key pressed while turning the knob.  But actually just keeping the key pressed for a few seconds changes from single channel to dual channel delay setting mode or back.

This is sadly typical of how most manuals are written.  And also how I forget the magic tricks I may have used before.