"search" agent selection option has disappeared from conversations under Copilot BlocNotes

https://support.microsoft.com/fr-fr/topic/utiliser-le-chercheur-dans-bloc-notes-microsoft-365-copilot-ea037537-30a6-45c4-84b6-84f32f6c75c2#articlefootersupportbridge=communitybridge

I used to be able to select the "search" copilot agent within Microsoft 365 notebook conversations (see example in the link), but it disappeared a few weeks ago. However, you can download significantly more documents in notebooks (limit of 100) than in the dedicated conversation with the search agent (limit of 20), and it doesn't retain the history in the same way. Is there any way to make it reappear?