Will TurboTax online allow me to delete a schedule (Quebec income tax return, Schedule D) once I make my payment & am able to review the returns before they're filed ?

TurboTax Online doesn't allow you to delete forms directly. You would have to go back to the provincial section and remove/change the info you entered for the Solidarity Tax Credit to change/delete  Schedule D. You can do this before or after you pay.

Can you please clarify the steps required to "remove/change the info" for the Solidarity Tax Credit? I do not know what changes to make to prevent Ttax from inputting into Schedule D. 

Go to the Tax Home page (2024 tax return on the left), and click on “Provincial”, then “Solidarity tax Credit”.