Value suggestion for attributes in segmentation is a feature that allows you to see and select the possible values for a text field when creating segment filters. You can enable or disable this feature for each data model object (DMO) field in the DMO record home. Value suggestion can be enabled for up to 500 attributes for your entire org. It can take up to 24 hours for suggested values to appear. To use value suggestion when creating segment filters, you need to drag the attribute onto the canvas and start typing in the Value field for an attribute. You can also select multiple values for some operators. Value suggestion is not available for attributes with more than 255 characters or for relationships that are one-to-many (1:N). References: Use Value Suggestions in Segmentation, Considerations for Selecting Related Attributes