Account Setup for Health Reimbursement Account?

I'm assuming that the "flow" here is that you incur a medical expense and pay for it out of pocket, and then later your employer reimburses you for this expense.

I would set up an off-line generic asset Account in Quicken for this. When you make the payment - let's say you use a credit card - the "other side" of the entry you make in the credit card Account would be to this asset Account, a "Transfer." When the employer reimburses you and you deposit the check in your checking Account, the other side of this entry would also be a Transfer to the asset Account, zeroing it out.