What is the best way to set-up test cases in a linear way

I find that a difficult question to answer without more information about your use case.  I'm not even sure what you're looking for but I'll take a guess that 'best way' with 'minimal structure' means you want it to be quick and easy.

You can add test cases individually using the interface, but I don't like using this option unless I'm adding the 1 or 2 test cases - it's too time consuming.  I prefer to import using a CSV template.

If this isn't the answer you're looking for please let us have more information