We had in an earlier version of the specification the following text explaining the intended usage (and decided in the team to deleted it):

A system integrator shall only be able to modify elements of a ConnectionConfigurationSetType instance as follows:

• The system integrator is not able to add or remove objects or variables from or to a ConnectionConfigurationSetType instance. He is only able to modify values, where applicable.

• The modification of content is not allowed for read-only elements. This may be related to restricted rights of the Client or as decided by the generator of the ConnectionConfigurationSetType instance. The right to access the current value of a variable is expressed using its AccessLevel and UserAccessLevel Attribute.

• The SelectionListType, as defined in OPC 10000-5, is used in many places, where modification is possibly mandated. This type allows providing values selectable from the Selections and an optional description using SelectionDescriptions.
  If the generator set the optional RestrictToList to value True, only values from the list can be applied to the element. With this, the generator of the data may restrict changes by supplying a list of accepted values. As an example, the PublishingInterval could be restricted to the values 2 ms, 4 ms, and 17 ms by adding these values to Selections and set RestrictToList to True.
  Setting RestrictToList to value False allows in opposite to apply any value to the element.

With these mechanisms the generator of the ConnectionConfigurationSetType instance is able to specify and restrict the allowed changes to it. He may even decline any change by setting all to read-only, or restricting all SelectionListType instances where Selections contains just one element. It is expected that an OPC UA Client will indicate the settings.

The SelectionListType indicates thus in most cases (besides booleans) the places where a possible change could be done by the system integrator. The intended usage follows the scenario defined years ago, a system integrator is able to adapt a existing CCS regarding addresses, and some other things of pre-downloaded connections, to tweak them for the use in his environment. For adding or removing connections he would have to use the engineering tool responsible for generating the CCS; this is not meant to be done through this interface.

need to look for boolean and make sure they are not selection list.

in call proposed to add part (or all) of the previous comment to the intro to connectionconfigurationsets

Added text to overview of connectionConfigurationSet, describing what is changeable and what is provided as options by an engineering tool

Other text was updated in the related mantis issue

Reviewed changes in call, agreed to text and closed issue