You can update the mapping of your import feed by navigating to Setup > Setup import in the left hand sidebar and selecting the Settings of the import feed you want to update. Now, click on the gear icon and then on update mapping. After confirming, the mapping of your import fields will be updated.
What does updating my import mapping do?
By updating your import mapping, the tool will check if there are any new fields that were not imported before and add it to the existing mapping. You can use this whenever you have added new fields to your import that do not appear in the mapping in Channable automatically.
Note: updating the import mapping will not remove any fields you added manually or change any other configuration you previously made in the "Edit mapping" tab of your import.