Installing map on the computer with garmin express

Possibly nothing.  Unless there is an update for the map on your Edge you won't get an option to install the map to your mac.

On a MAC the option is available to reinstall a map to the device and to the computer. That said, not sure why the OP does not get that option at all. Just wanted to correct your statement that the option isn't available - I see from other posts you state you're not totally familiar with the MAC interface.

You're confusing things.  There is only an option to 'reinstall' a map if you've installed it in the first place.  The reinstall option doesn't appear therefore for a map that originally came with a device, hence my comment.  This is true both if you are using a mac or windows.

I read it differently.

Fair enough, interpretation is everything in this game when you're trying to second guess what some posts mean 

Thanks for the comments. I saw the option in a tutorial in YT and was supprised Boy the option missing in my App. I‘m Not sure if the reason that the tutor uses a different device (for Motor bikes) and maybe that explains the difference. 

Anyway, I can access to the maps installed on my device in the app, so at least I can create routes. Installing the map locally would have been nice though.

You could always copy it to a removeable drive or create a virtual drive so you needn't have your edge connected

http://www.javawa.nl/virtualdevice.html