Only in the desktop software.
In the desktop software, if you prepare your full 2018 tax return there, you can either:
1) make a second copy of your 2018 tax return and change all your values to mimic what you expect for 2019
or
2) Open your real 2018 tax return....a) switch to "Forms Mode" b) Open a "What-IF" worksheet c) copy your 2018 data into each of 3 data columns (just need to check a box and all the data copies over to a new column) and then d) change the data in each of the columns to model different income situations for 2019.
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*