I am using XmDropDown instead of XmComboBox, since I prefer its look and feel, and setup is easier.
But I have problems with keyboard bindigns, which I find extremely unintuitive.
Ctrl+"arrow down" to pop up the list and Ctrl + "arrow up" to closes the list.
And "Enter" with the list open does not confirm the choice?
But "Esc" correctly closes it.

The man page does not mention any translations or accelerators, like in XmComboBox man page.
I have looked a the source, and can find only the following
static char combo_translations[] ="#override \n\Ctrl osfDown: XiComboListPost()\n\Ctrl osfUp: XiComboListUnpost()\n\Any osfCancel: XiComboListCancel()";
Xi prefix is strange enough for a standard Motif widget. And anything I try to override translations does not result in changed behavior.

I would like the arrow up and down (or mouse wheel) to rotate/change the list entries directly, without opening the list. And if the list is open, I want it to close on Enter.
I can also accept any other "standard" behavior, that is keys which other toolkits are using for these kind of widgets. For example, Qt uses arrow up and down to rotate among values, Alt + "arrow down" to open the list, then arrows up and down to navigate the list, and Enter to confirm.

Any suggestions on how to solve this matter will be greatly appreciated.
Otherwise my most productive users will curse me.