Hi Lukasz,
Greetings from Syncfusion support.
We would like to inform you that you can enable editing for only one column/row in Grid at a time, this is the default behavior of Normal mode of editing in Grid. We suspect that your requirement is to display checkbox for all the Boolean column values in Grid rows. If so, then we suggest you to enable the DisplayAsCheckBox property in GridColumn, this will display checkbox for bool columns based on the Boolean values.
Please refer the codes below,
Please get back to us if you need further assistance.
Regards,
Renjith R