This is not possible as such. Grouping works by comparing some values on a specified column, and assigns rows to groups according to the result of this comparison.
Therefore, the only solution we see is to have an hidden column, on which you could arbitrarily set the cells values to value that would create a group. So the SelectedRows corresponding cells would be set to a unique value that would identify their group, and all other rows would keep the “non-group” value, though this would create a group (the unselected rows group). Then, if the user selects new rows, you can again set the new SelectedRows corresponding cells to a new unique value, which would again create a new group. At this point, you would have 3 groups. etc…
See our help documentation to learn more on custom grouping :
Imported from legacy forums. Posted by André (had 1952 views)