Currently we already have created scripts in Katalon around 200+ and we used hard-coded test data credentials on each EPIC test cases e.g. log in, etc…
I would like to know if which more convenient to use in terms of regression
Hard coded data or
Test Data excel file (this will burn another effort to do so).
Test data all the way. It might feel like alot of effort to do so but trust me it will be worth it in the long run. Now i dont know what kind of product your testing or the lenghts in which you have to test the product, but for me personally, its made the process much more efficent. Especially if you have multiple tests doing the same thing just with different sets of data casusing different results its a no brainer.
Please read the link that me and Arnel have provided. Data binding will allow you to run the different sets of data in the suite. It explains it all in the doc and gives you steps to follow.
Now the difference between the input and variables is that the variables will allow you to pass through multiple data sets. This will make more sense when you have set up the data binding correctly as the variables are brought through into there.