You may want to investigate the Macintosh application GarageSale.
Its light years ahead of anything eBay will ever offer.
Select the items in the left column, click in the center preview column and select all the items, then make your changes using the Options, Advanced or Properties tab.
If you want to make changes to multiple descriptions you can use a custom AppleScript.
If you want to make changes to standardized text that you place within each listing, such as your TOS statement at the end of the listing, then simply edit a Text Snippet representing that insertion and its changed for all listings using that bit of text.
Everything is stored on your computer and not eBay.
