The virtual keyboard/text field input modes indicate user defined and built in sets of keys/maps. This set of strings indicates the name/order of the input modes which will toggle, if only builtin modes are used no further action is needed.
However if a custom input mode is desired then the input mode itself must be defined as well specifically by defining an attribute called @vkb-InputModeName or @im-InputModeName for a text field input mode.

The following input modes are builtin to the VKB:

The following input modes are builtin to the TextField