Hello Barthelet Thibault, Welcome to Microsoft Community. I realize that you've encountered a problem with removing add-in in Word Online, and I understand how you feel. Please feel free to correct me if my understanding is wrong.
In order to solve this problem, please try the following steps:
- In the Home tab, find Add-ins and click it. (Yes, as you mentioned, it is here now.)
- Click More Add-Ins.
- Click MY ADD-INS. Find the add-in you want to remove and click on the three dots to the right of it.
- Select Remove.
- Click Remove. Then it should be removed successfully.
Please let me know if the result fit your expectation. I'm looking forward to your reply.Best wishes,Lucia Wu - MSFT | Microsoft Community Support Specialist