My floor drain is 12" off the floor. How important is it to install a syphon break when hooking up my new washing machine

If your floor drain is 12" above the floor it's not a floor drain. Most drains for a residential washing machine will be roughed in at 12" above the floor and then using a short pipe nipple and a trap you bring a stand pipe up past the washing machine and then hang your hose in there. Yes, by code they want a separation from the hose to the pipe and you can buy a special little plastic piece to do that but most people just put the hose inside the pipe and sometimes the just hang it over the side of a laundry sink basin. The one thing you need to know is that it is secure and doesn’t come away from the point of entry and create a flood. That would be bad. So if that is a concern be sure to secure the hose firmly to the drain.

I am little confused with your terminology. Can you describe your situation in different way ? Perhaps, take photo and post it ?

My floor drain is 12" off the floor. How important is it to install a syphon break when hooking up my new washing machine

I'm thinking a washer stand pipe that should be increased by at least 2 feet.
Let's trade the term "siphon break" for "air gap" or "indirect waste".
When you hang the washer hose over the pipe you have just made a "siphon break" so you need have no concern. Good luck and add a couplingt and a 2 foot piece to the pipe. Tom