Symptoms

Change Control button does not have List Display for Text or Yes/No datatypes without setting up associations between SmOs.
 

Diagnoses

Without setting up SmO associations List Display works only for Numeric data fields.

According to K2 documentation you always have to have SmO associations to use List Display control:

"When dragging a Field of type List Display onto the canvas, the properties displayed will be specific to that Field. A List Display needs to be bound to a SmartObject containing an association to another SmartObject. To populate a List Display a transfer data Rule action has to be configured to pass the relevant value to the List Display."

Source: http://help.k2.com/onlinehelp/k2smartforms/UserGuide/current/default.htm#SF_-_ViewControls_-_List_Display.html

But actually when designing a view you can click on list view column, then click "Change Control" button and select List Display control and then select display field from another SmO without any associations in place in case column data type is Numeric, but for Text or Boolean (Yes/No) it works only when associations are configured.

Use case for such functionality in large solution: you may have SmO which contains display values for multiple other list views which use either Text or Boolean column with value code but it is required to provide some other display values from another SmO which contains them. E.g. you may have Text column with country codes (RU, US, SA) and want to pull country names (Russia, South Africa etc.) or you store 1/0 but want to display "Contract Approved"/"Contract Rejected"

Currently you have to create numerous SmO associations to support this (in case you need to link display values SmO to numerous other SmOs) and apart from loads of manual work to create associations it causes issues with deploying this solution via PnD as your Display Values SmO when included in packages automatically pulls all associated SmO which use it even if they are not really necessary.

 

Resolution

Described behavior is expected in all current versions of K2 including upcoming K2 4.7 release.

There is also an existing feature to allow the use of the List Display control for Text/Boolean columns in the same way as it works for Numeric columns i.e. without creating SmO associations (internal ID 692363). There is no ETA for implementation of this feature request at the moment but clients interested in this functionality encouraged to log support tickets so that this item can get appropriate priority.