You can include one test inside another one: for example if you have a procedure that takes 5 steps to log in to your system, you wouldn't have to repeat these 5 steps over and over.
If a step contains the prefix
followed by a test case, or use case, the generation of the test execution form will include all the steps from that sub test inside of the step with include
Here is the test case TC-5
Here is UC-4:
And here is the generated test execution form :
You can of course enter different UC and/or TC in the same main TC.
Note: if you want to make use of this feature, it's recommended to put make a new category to a hold a library of reusable test snippets. Putting them in a specific library will avoid traceability issues.