Check your by-laws but it is likely that the vacant car space can only be used for some type of vehicle storage. It should not be used as a work shop or as a general storage area. This would be a change of use from the original Development Approval.
A work shop in a designated garage space could breach many regulations and laws including: fire safety regulations, appearance of a Lot, health and safety, use of common property electricity, nuisance, noise, damage to common property etc etc.
Jimmy T alluded to it here: https://www.domain.com.au/news/parking-cages-in-strata-buildings-raise-ire-of-other-owners-20160310-gnci4q/
Perhaps you could explore the option of having a work shop offsite, perhaps in a “Men’s Shed”, if there is one in your area.