Do I need to mail PA-40 Line 1a Gross Compensation Worksheet with my return?

No, you don't need to mail your  PA-40 Line 1a Gross Compensation Worksheet with your tax return. In general you mail in the forms, but not the worksheets. 

This is a complete list of what should be included in your PA tax return from the PA Department of Revenue:

• Original PA-40
• Federal Forms, W-2, 1099-R, 1099-MISC, 1099-NEC. 
• 1099-R, 1099-MISC, 1099-NEC and other statements that show other compensation and any PA tax withheld. NOTE: Do not include copies of Form(s) 1099-DIV, and 1099-INT, unless the forms show PA income tax withheld.
• PA Schedule OC, and the required supporting documents when claiming any of the restricted tax credits that PA law allows.
• PA Schedule(s) RK-1, PA Schedule(s) NRK-1. If you did not receive PA schedules, then submit federal Schedule(s) K-1. 
• PA Schedule(s) G-L. If you are claiming a resident credit for taxes paid to other states, include each schedule followed by any required supporting documents for the schedule.
• All other required PA schedules and forms.

Thank you Julie for your thorough answer.  It was very helpful.