For my dependent child under 18, thereis a box that says Total Income Split from Line 6836 of Form T1206. Do I put what she earned there after entering her income?

You only need to enter that information if your child had to fill in a Form T1206 (Tax on Split Income) on their tax return. T1206 only has to be filled out if a person has certain non-employment income from a family member. Most people don’t need to worry about the T1206, and if your child doesn’t need to put one on her tax return, then you can leave that spot blank.

Here is a CRA FAQ on the tax on split income (TOSI): https://www.canada.ca/en/revenue-agency/programs/about-canada-revenue-agency-cra/federal-government-...