To update/edit titles and descriptions via bulk, go to IMPORT in the console and upload a CSV File ( just like importing items). Please see the sample below. It should look like this with the headers Asin, Title, and Description.

If you want to update just the title, upload a CSV same as above with the headers, input the revised title, and leave the description column blank and vice versa. It should look like this.
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Upload the CSV File, put a NAME, choose the SUPPLIER, choose UPDATE LISTING, pick the correct eBay account, and click SAVE.

IMPORTANT NOTE:

You should only update titles/descriptions per eBay account since you will need to choose an account in the dropdown. For example, you wants to update titles/descriptions for eBay X then the items in the CSV file should only be for eBay X and no other items from other eBay accounts.