If you are still keeping residential ties in Canada while living abroad, you don't file as an emigrant, nor you specify the date when you left Canada. You still have to file your taxes as a Canadian resident:
https://www.canada.ca/en/revenue-agency/services/tax/international-non-residents/information-been-mo...
If you have filed your return as an emigrant, then you will need to file a T1-Adjustment and add in the comment section the reasons for this request.
For more help, contact the International Tax Services: https://www.canada.ca/en/revenue-agency/corporate/contact-information/international-tax-non-residen...
I hope this was helpful
