The $1,200 standard amount was added to Chart B, Column 3 in 2021, with small changes to the T2222 form being made since then. The form from 2020 specifically said "You can claim a deduction for medical travel if you have an amount in box 33 of your T4 slip or box 116 of your T4A slip showing any taxable travel benefits you received in the year." But what hasn't changed is that Chart B looks for the lowest amount in columns 3, 4 or 5. So, if Box 33 is zero, and you have used up the $1,200 standard amount on other trips, then column 3 is zero, and that's what's going to be used in the totals for Chart B.
You can see the current (2023) T2222 and the previous versions of the form on the CRA website: https://www.canada.ca/en/revenue-agency/services/forms-publications/forms/t2222.html
