In an experiment or notebook field created using an attribute linked to an external list now there is the option to select multiple values. This change needs to be enabled in each field manually.
Solution: To enable a multiple value field for an external list attribute in an experiment please follow these steps:
1. Navigate to 'System Configuration' > 'System Objects' > 'Experiment' > 'Templates'
2. Select the experiment template to modify the field to allow multiple values
3. Go to 'Fields' click on the 'Edit' button for the field
4. Mark the checkbox for 'Multi Select'
5. In the 'Default Value' text field choose predefined values if desired