Click the three dots next to your catalog name and click Import Highlights. Select the conversation or full collection you'd like to import highlights from. Click Submit.
Removing highlights from your catalog:
To remove highlights from your catalog, click the three dots next to your catalog name and select Remove Highlights. From here you can select the name of a conversation you'd like to remove. Note: Removing highlights from your catalog will also remove (and delete all tags) from all of the highlights from that conversation.