In the workflow settings, can you uncheck the “Show grid lines” and click OK, and then go back to the workflow settings and check it again and click OK?
No problem @ArjenEX , I’m glad it’s resolved. Did you by any chance shut down your computer (or reboot) overnight? If that’s the case, it could be that you were running out of memory, and by restarting your computer, memory was back to normal and Knime was able to display everything, including the grids.