collapse all and expand all functionality over a button for matrix

Hi, sanjanarama 
Way 1: Drill Up and Drill Down
With this way you don't even need to create additional buttons.

Drill down and drill up in a visual

Way 2: Bookmarks + Buttons
Create bookmarks to record the expanded and collapsed state of the matrix, and create buttons to link to the bookmarks.
Create report bookmarks in Power BI to share insights and build stories

Result:

Please refer to the attachment below for details.

Hope this helps.

Best Regards,
Community Support Team _ Zeon Zheng

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