Select Multiple Nodes in custom module

Is there a way to either use a qMRMLNodeComboBox to select multiple nodes (in my use case, Markup Nodes)? I am trying to use the qMRMLCheckableNodeComboBox, but am having trouble connecting it to between the GUI and the process logic. I am using a ParameterNodeWrapper for other parameter input but not sure how to either manually connect the Checkable widget or if there is a better way to get multiple input nodes.