You can break blocks in creative with a sword by doing the following steps:

1. Have a non-sword item in any slot
2. Break a block while holding it
3. Use 1-9 to switch out the item with a sword
4. You can now break blocks while holding a sword in creative
Video of bug: https://youtu.be/mSzJPahOLE8

Sorry if it's a duplicate, but I couldn't find a similar report due to all of the duplicates of the "Swords not breaking blocks in creative"