The import via SAP Solution Manager connector into Signavio, creates a separate dictionary entry for every single SAP transaction. If you want to attach more than one dictionary item to an attribute in Signavio, you need to define this attribute "as list" first. Here you can find a description how to do this: https://docs.signavio.com/userguide/editor/en/workspace_admin/manage_modeling_settings/configuring_notations_and_attributes.html#defining-custom-attributes
Please note that after creating a custom attribute, you cannot edit its data type and its "As list" option any more.
In case you want to map an attribute defined in Signavio "as list", the mapped Solution Manager 7.2 attributes have to be of the type multivalue. More about how to configure attributes in Solution Manager you can find in the SAP blog: https://blogs.sap.com/2016/10/31/create-customer-attributes-elements-process-management-solman-7.2/