How many 2023 TT can I install for one account? I have a big family and 5 E Files is not enough, so can I buy more TT versions for one account holder?

No.   The five federal e-file limit is an

IRS limit.  

So within your family, decide whose tax returns get e-filed and whose returns get filed by mail.  After you e-file five, the rest must be filed by mail.

Thank You