CRA requires you to wait until you receive your Notice of Assessment before making any changes to it for a number of reasons. Often times you may have submitted/NetFiled your return and CRA catches the error or missing slip and corrects it for you before assessing the return. If they do make any changes or corrections to the return you filed, it will say in the Notice of Assessment you receive.
Once you receive that NOA, you can proceed with your T1 Adjustment if necessary.
https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/change...