Cannot add Test suite to Test Suite collection

I have mobile and web test cases and both test cases are dependent to each other. In some we need to run mobile first and in some case web then verify or do some execution on other platforms.
The problem is I can not add Test suites into Test Suite collection.

Katalon Studio version:-
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Katalon team any help will be grest.

You should be able to make this:

├── TestSuiteCollection
   ├── TestSuiteForMobile
   │   └── TestCaseForMobile
   └── TestSuiteForWebUI
       └── TestCaseForWebUI

It seems you have not yet createted TestSuites. I mean, this:

├── TestSuiteCollection
   ├── x
   │   └── TestCaseForMobile
   └── x
       └── TestCaseForWebUI

Have you?