The best anti-theft measure is not having a thief target your bike at all. Make your bike look the least appealing of any at a bike lockup. Cover it in tape, ratty stickers, put a plastic grocery bag on the seat with rubber bands, hang empty fast-food containers off the handlebars, etc. Also remove anything that can be removed without tools such as wheels, seat, and any electronic control devices. If your battery can be removed then pop that off and take it with you. An ebike without a battery is hardly worth stealing when there are other options.

If possible - keep the bike inside but if you absolutely must use a parkade regularly I would strongly consider avoiding a new bike. A brand-new, shiny ebike left unattended (especially in a parkade with a theft problem) is just begging to be stolen.