I'm just over 5'-6" with a 28" inseam and this has really been a challenge for me too. Here is what I've done:
1. I had Spencer to lower my seat and add the long distance gel core in it. This seems contradictory, but I put my seat height selector in the middle setting and force the seat to go into the lowest setting on the back tabs which gives the seat a little more tilt rearward. I don't understand the dynamics, but I can reach the ground better like this than I can with the front and rear both in the lowest setting. The Spencer seat mod was only like $100, so it's an inexpensive modification.
2. I cranked the preload on the shock down to as low as it will go and still be secure without the knob coming off. This allows the suspension sag to drop a lot when you sit on the bike which helps get you to the ground, but it be aware it also negatively affects the handling characteristics because the ride is really soft and mushy when cornering. If you do this, you have to remember to crank the preload back up when carrying a passenger. Hey, a free adjustment!
3. I got a nice pair of hiking boots to ride in because they have roughly a 1" thick sole that helps fill the gap from where the seat lowering and suspension adjustments fell short. While these may not have the "style" of a motorcycling boot or win you any points in a rider's fashion show, they're waterproof, have superior ankle protection, and can be worn casually when not riding.
While I wish I could put my feet feet flat on the ground, these adjustments have made it possible to where my heels are now only about 1/2" off the ground. It's not optimal, but it is much better than it was. When parking, I just make sure I park facing uphill which means some times I have to back into the parking place. I also pay close attention to where I stop my bike to make sure I don't stop where there's a low spot between the wheels beneath the seat. That's disaster. Whenever possible, I place my front wheel in the gutter when pulling out of parking lots which places a hump between my wheels and I can then flat foot the bike.
Good luck and hopefully these ideas will help.