Currently many Brokerages (ETrade for ex) charge margin rates as high as 13%+. If you need temporary margin you can sell a stock short and buy a call and raise cash. Not sure how Etrade treats it. In IBKR you get credit for the cash and it offsets any margin debt. On Some ETF’s you can raise cash this way at 4% to 5% annualized vs 13% or so.
As expected E*Trade sets aside that cash as short reserve and your margin debt is not reduced… sad but not surprising or unexpected.