Hi @Willem Koopman ,
Currently there are no Microsoft Graph APIs available to add/get/delete attachment for To Do Tasks resource type either in V1.0 or beta. As per this MS documentation , attachments propery and related methods are planned to be added to Microsoft Graph To Do APIs in future releases. Incase this is a priority requirment for you, you can submit this feature request idea using this support link, which will be monitored by Microsoft team and make the enhancements to Microsoft Graph APIs. At present, attachements can be added to To Do Task from TO DO UI after the new task creation.
Below is the screenshot form this Microsoft documentation :
Adding attchment for TO DO UI for the exisitng task:
Please refer the below documenation links for more information on the current supported methods and properties of Microsoft Graph To Do API :
https://learn.microsoft.com/en-us/graph/api/resources/todotask?view=graph-rest-1.0
https://learn.microsoft.com/en-us/graph/api/resources/todotask?view=graph-rest-beta
https://devblogs.microsoft.com/microsoft365dev/the-new-improved-microsoft-graph-to-do-apis-are-now-in-public-preview/
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