I have three task list on three subsites of my main sharepoint (sharepoint online). What I would like to do is "overlay" like you can with the calendar, but instead the list in list form so it can be viewed as a Gantt chart still. Essentially I'd like to pull the three Gantt charts (task list) into one master Gantt chart that updates as they do. Is this possible?
I understand that you want to show all the tasks in multiple site into a single task list .Here are my suggestions :
- Create a publishing page layout .
- Insert the content query web part
- Customize the query .
In this way you can display all the tasks in a single web part ,but you cannot connect this web part to Outlook .You have to manually connect task items to outlook one by one .
There is another workaround. You can create a task list to save all the task items .And create an event handler to copy the task items to this new task list when the user creates\update the item. Then you can connect the new task list to outlook .
For more detailed information, please refer to this site: