I agree, I don’t think you are missing something, @Bastien_Siebman
Hi @Dea_Marušić , welcome to the forum
I see you post this in the AI Studio category. Are you trying to create an AI studio Rule? Or trying to get an answer from the in-product AI chat bot?
You can’t do this natively in Asana unless you were to run an advance search report or view dashboard charts on the last day of each month and store them.
Maybe the Sync to Google Sheets could allow you to do this with a macro and other tabs in GSheets or Excel?
Or perhaps with Business Intelligence tool integrations.
@Dea_Marušić you can do that with the Screenful add-on. You just need to select the Deal stage custom field as the workflow field. After that, Screenful keeps a record of the historical changes to that custom field and you can create a chart (e.g. table) that shows how many tasks were in any of those stages at any point in history.