How do I insert statements allocating interest, dividends and capital gains for before and after death of the taxpayer?

[MichaelL1]

You can't with a e-filed return.

IRS knows that these documents will not match in year of death.  

If you want to submit them to IRS with the return, you will have to paper file the return and attach them.

The whole key, is making sure 100% of the income is reported of which some may be on 1040 and some on the 1041 return or the beneficiaries' return.