Given that it’s a rented property and you’re not likely to want to make expensive permanent or non portable changes I would do the following:
Asgard bike store (or similar) kept inside the garage. Keep all cutting tools either inside the asgard or preferably in the house.
Position the asgard so that it cannot be in plain view from the windows, so that at a casual glance it is not easily identifiable.
Set a ground anchor in place below the asgard (you may need to cut a whole in the base of the asgard) and use a 19mm security chain to lock the bike inside the unit.
If the garage has power try and isolate that and get in the habit of not leaving power to the garage when not in use. It’s not unknown for thieves to break into neighbouring sheds and garages to nick tools so there is no need to supply them with the electricity to use them.
Finally fit a shed alarm.
If it were not rented I would also look at changing the garage door and adding bars to the inside of the windows.
There is no way to stop a determined thief that specifically want what you have but you can deter a large percentage by making it so awkward and time consuming that they will move on to a softer target.