So this issue still hasn't been fixed in over a year? 

Sales Tax Prepayments still can not be entered for Quarterly filers in the Sales Tax module.  It seem unreasonable to expect people to wait months to enter the Prepayments or enter a Journal Entry that would then need to be removed and re-entered in the Sales Tax Module.  Prepayments are standard in California and we need a way to post these payments in real time and have them reflected without duplicating work. 

Please bump this up the priority list for QBO to resolve ASAP.