Fernando Welcome to Microsoft Q&A Forum, Thank you for posting your query here!
AFAIK, this option is not available in the deployed Web Apps.
I saw in this guide that there was a + button, presumably allowing for image uploads: https://techcommunity.microsoft.com/t5/educator-developer-blog/deploying-gpt-4o-ai-chat-app-on-azure-via-azure-ai-services-a/ba-p/4179472
I just tried and not able to see the option that you mentioned.
The Icon which you are referring to is a new chat option.
In order to modify the Web App, please check Sample WebApp and make changes accordingly.
I hope this helps. Do let me know if you have any further queries.