In our (desktop) application, we have two different families of selection fields. Some can open a dropdown dialog (combo boxes, date fields which open a calendar in the drop down), and the others can open a selection dialog instead. The latter looks like this:
For the dropdown fields, we use ArrowDown as a keyboard shortcut to open the dropdown popup.
For the fields which open a dialog, we're yet unnsure which keyboard shortcut to use to open the dialog. The button which opens the dialog cannot be reached with tabbing (all our fields have only one component that can be reached by TAB, the next TAB will always leave the field).
What's the appropriate keyboard shortcut in this case? Whould we use ArrowDown as well, or rather some other shortcut such as Enter?