I am wondering if it is possible to do something in TIA that I am able to do in Rockwell which is call an input based on a created variable. as an example in Rockwell I can call I3.0 by doing the following I[int_variable].0 where int_variable = 3. Is this possible in TIA portal particularly in STL. Thanks

Yes, indirect addressing can be done in TIA Portal using SCL (easier) and STL. The syntax is very important and capabilities vary between families of CPU's, so refer to the Siemens programming guide for your specific model CPU