CRA allows all employees who worked from home during the COVID-19 pandemic in 2020 to claim up to $400 in employment expenses at a flat rate. This amount is a tax deduction and not a credit, which means you deduct it from your income to reduce your tax liability but will not result in a refund. 

Expenses related to a home workspace can be included on line 22900 but there are considerations to review with the new allowances and possibilities available due to Covid 19 this year.  Here are Canada Revenue Agency links with information regarding Expenses Tax Info Centre   CRA  Eligibility criteria - Temporary flat rate method 

Note: For the flat rate method to be activated in TurboTax Online, you enter your T4 and scroll down to the bottom where you will be asked: Will you claim employment expenses for working at home due to COVID-19 for income on this T4? NEW! You will then click on Employment Expenses found lower in the menu on the left side of the screen to then answer yes on the right screen. On the Employment Expenses Profile page, check the option: I didn't receive either form from my employer. On the next screen Check the flat rate method and enter the number of days you worked from home.