How can I connect mac to Iphone hotspot without making "personal hotspot discoverable"?
Unfortunately many useful settings on iOS are simply not there.
One of this is the inability to hide your SSID.

If you really care about security you should just use the USB cable, to force this you have to completely disable both Bluetooth and Wi-Fi from you settings and then enable the hotspot.
It will ask if it's okay to only share your cellular connection with the USB.

Otherwise you can just use a strong password, if both computer and iPhone are up to date you shouldn't worry about anything. WPA2 is very secure and KRACK was patched a long time ago.

Even if you could hide the SSID everyone you should worry about can still see your hotspot. There is no way to hide any wireless connection.