If GA was your home state for all of 2018, it taxes all of your income, regardless of where generated.

That doesn't answer the question.  I am able to deduct income from other states off my Ga income taxes, however, I can't select Texas from the list but I can the other states including Tennessee that also doesn't have State taxes

Why are you deducting other states' incomes from GA?  That is not permitted if you are a GA resident.
(and TN has a Hall tax.)

And maybe I stated my original question wrong.  It's called 'Other state tax credit' - you can deduct the taxes you paid in other states, but you have to put the income and taxes paid.  You can enter every other state including Tennessee which has an Excise Tax.  Texas isn't an option and it has a margin tax.  SO my question is why isn't Texas on the list?