Hello Sven Persijn,
On the follow up of [DataGrid] Losing selected lines on right click and following the requirement that you asked in order to have a blue overlay on the row of the cell that you are selecting, here goes a workaround solution in a sample format just to illustrate how you can accomplish that specific behaviour. Can you please check the sample attached to this message?
As a workaround, you can use the sample as an example. You will need to include a Web Block containing the methods that you want to replace in order to have the overlay on the rows. (This block is included in the sample attached)
Inside the Web Block you can see that we have a Javascript block containing two methods. Right now the only way we have to create the behaviour that you want is by overwriting two methods from our component.
GridOS.DataFeature.loadFeatures
GridOS.ExtendedFeatures.ExtendedSelectionManager
So please note that the methods mentioned above are getting overwritten.
Feel free to change or create your own method.

We also need to add a class into the css from the sample:
This class will be responsible for the color that is going to be on the row's overlay after selecting a cell. You can change the color by changing the background property.
Hope this sample is useful if you need to extend DataGrid to add a color overlay on top of the rows where a cell has been selected.
Thank you,
Tiago Pereira