What is the purpose of the checkbox ‘use relative path for image’ in object repository
It is used for Image handling keywords. Relative path is within project, so if absolute path is C:\Katalon\YourProject\img\test.jpg, relative path would be img\test.jpg
https://docs.katalon.com/display/KD/[WebUI]+Verify+Image+Present
https://docs.katalon.com/display/KD/[WebUI]+Wait+For+Image+Present