The Previous Day Key Levels indicator plots the prior trading day's High, Low, and 50% retracement levels on the chart. Users can customize the display by enabling or disabling historical data and selecting the number of past days to view. The indicator allows color customization for each line and the option to show or hide labels identifying each level. It supports various markets and symbols including Forex pairs (EURUSD, GBPUSD, NZDUSD, USDJPY), cryptocurrencies (BTCUSD, crypto), commodities (XAUUSD, gold, oil, silver), indices (NAS100, Dow, S&P 500, DAX), and stocks. This tool is designed to assist traders in identifying key price levels from the previous day that may influence current market behavior.