Sorry for your loss. Pension splitting can be performed in the year of death, however, it is a pro-rated calculation based upon the date of death. You'll need to prepare your husband's tax return first, then use the information from his return to complete your return so his Disability Tax Credit transfers to your return. 

TurboTax will guide you through the steps to ensure you get all the credits you are entitled to. You must be sure on your own tax return, in the My Info - Marital Status section, you specify you were Widowed, and say "Yes" to the question "Did your spouse/partner pass away in 2018?"