Hi, there are a couples of ways to do this, here are 2 ideas:
One of the more obvious ones is to use the default Mendix group box widget in combination with a list view.
You start of by showing the desired attributes above the groupbox or in the groupbox header. The rest you can show inside the groupbox. With some styling you can let the listview look a bit like a datagrid.
Another solution would be to ‘ hide’ columns by default and let users add them if they wanted to, this is possible for example with this widget https://marketplace.mendix.com/link/component/2702 (will also be possible with datagrid 2.0 in Mx9)
One of the solutions is to use a listview with hover option as available in SASS. At the moment you hover over the entity you expand the view. See below on an example I made:
You can also enlarge the area that is visable via Sass.
I hope this helps.