This is a must. We have lots of Office 365 Groups, but they don't all need to be in PowerBI. A simple "Right click > Hide" would be nice.
In general, a mechanism to select which O365 groups are used in a particular O365 app would be very useful.
O365 groups are probably here to stay and provide a lot of functionality for collaboration in organizations.
I do agree that using groups in this intended way ends up spamming ones Power BI interface to the point that it gets too busy and difficult to find the groups that actually contain Power BI content.
Please provide an option to hide/organize groups to make it easy for finding our dashboards and reports without scrolling past many empty groups with no Power BI content.