The ability of this setting to "wrap" as others do was removed for volume with a commit on the 6th november of last year to prevent accidentally going from lowest volume to maximum - it wouldn't have been that critical the other way round but I guess it's only all or nothing.
I just had an idea that could work without compiling, though redefining the button mappings and compiling your own build is probably more comfortable. Anyways the idea is to work with a few prepared config files, which only contain the "volume: xx" line to set it - where "xx" is decibels (from "-73" as minimum to a maximum "6"). Then you could go through the menu "Settings > Manage Settings > Browse .cfg files" and choose for example your "volume-40dB.cfg". All these menus and lists should be browsable with only going upwards. I think you can find a bit more info about how to work with config files in the manual.
Edit: the stated numbers are X5 (M5) specific and I was just naming the possibilities

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