Where do condo maintenance fees go when claiming home office expenses? Under GST taxable or HST taxable? and what falls under the exempt column?

You would choose which column to put the expense in based on whether you paid GST or HST on the expense. 

This CRA page has examples of whit is Exempt/Zero rated: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/gst-hst-businesses/charge-collect-type-supply.html