hi,
Sorry not read clearly your issue 
you have already used CSS Selectors
try to use CSS Selector as locator
in browser
inspect → copy → CSS Selector
and use javascript
String js = ‘document.querySelector(“#my-button”).click();’
WebUI.executeJavaScript(js, null)
some info will found here
http://forum.katalon.com/t/how-to-groovy-javascript-css-using-css-selectors-in-javascript-in-groovy-in-test-cases/34488