So I tinkered around with it and fortunately 🤗 found a workaround to this problem. Instead of importing the .txf file from the Step by Step interview when it prompts for it in the Investment and Sales section, import the file from the File menu by selecting "Import-> From Accounting Software". Importing the file through this method will import all the sales categories too for each transaction. Only the name of the broker won't be imported. Manually enter the enter broker's name in the corresponding Form 1099B Worksheet by going to "View->Forms". Be sure to enter the broker's name manually only by this method. Doing it through the Edit option of Investment and Sales in the Step by Step Interview will make the sales categories disappear again! 😮
My brokers are Interactive Brokers and TD Ameritrade and what I described above worked for both brokers, so I am pretty sure that it will work for other brokers and banks too as this issue appears to be a generic Turbo Tax .txf import bug (when done through the Step by Step Interview 🤔) instead of a broker's file specific issue.
