I have multiple Facebook accounts linked to different Facebook Ads users. How to link all of them?

Create a Windsor.ai account, Go to Facebook Ads and click Grant Access and log in with the first Facebook Ads user. Now you should see add accounts appearing. Click Grant Access again. Now you should see accounts which are linked to the first and second user. Repeat this process until you have all the accounts you wish connected. To select which accounts will appear in your reports (e.g. Data Studio or Power BI), select them in the dropdown.