How can I use a method define in 1 testcase into another testcase?

I defined 1 method “boolean waitForElement(def element, def seconds)” in one test case & I can use it in the same test case without any issue but when I call it from another test case I get below error:

Test Cases/Common/Gmail Login FAILED because (of) groovy.lang.MissingMethodException: No signature of method: Script1527664783509.waitForElement() is applicable for argument types: (com.kms.katalon.core.testobject.TestObject, java.lang.Integer) values: [TestObject - ‘Object Repository/Common/Page_Gmail/input_password’, …]

Test Cases/Common/Gmail Login.run:32

How can I use a method define in 1 testcase into another testcase?

You can create Custom Keyword in Katalon, include your method and then you can reuse this method everywhere in your project.

So that means there is no way to use a method defined in one test case into another test case except creating custom keyword?

I am afraid there is not.