Multiple row selection on CTRl + Mouse click and SHIFT + mouse click.
Hello,
We have such issue logged in our GitHub repository with label "feature request". You can add a comment there as well:
https://github.com/IgniteUI/igniteui-angular/issues/3654
As for the Ctrl + mouse click functionality, this comes by design with our multi row selection, by using the checkboxes on the left:
https://www.infragistics.com/products/ignite-ui-angular/angular/components/grid/selection.html
Let me know if you have any further questions.