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There are two ways how to group projects by their names.
One option is creating new calculated members in Project dimension where you aggregate projects based on their names. A separate calculated member for each group (AA, BB, CC) must be created. The calculation formula for such a member would be the following, example for a group of reports starting with AA
[Project].CurrentMember.Name MATCHES "^AA.*"
Use those members in the report instead of projects.
It works well if you have a few projects (it is doable to create members, as well as the report performance is affected treatable).
If you have a lot of projects, another option is to additionally import the project group name to each Project dimension project as a property, and then, based on that imported property, create a new hierarchy in the Project dimension. Then you would use this project group in reports instead of the projects.
Here is described how to import additional data: Additional data import into Jira Issues cube - eazyBI for Jira
And how to create a custom hierarchy based on properties: Create reports - eazyBI for Jira
You may watch a video about how to import such properties and then creating a report based on that: Training videos on specific topics - eazyBI