When building a segment, you need to enter a long list of values for a rule. Bulk edit allows you to enter a comma-separated list of values rather than force you to pick out what you need from the Attribute Values list.
How To Bulk Edit Attributes
1. Choose the Bulk Edit option when adding attribute values to segment rules
2. Enter a comma separated list of values (note: only valid values will be saved). Then select the 'save values' button.
3. Include the recency and frequency (if applicable) and choose the 'add rule' option to finish adding the attribute values to the segment rule
4. Once complete, you will now have a rule containing the comma-separated values you entered.