The Horizontal Reference line tool has an option entitled "Bar Lines". This option gives the user an automated tool that draws horizontal reference lines at 6 levels: current open, current high, current low, previous open, previous high, previous low. This option comes with a periodicity control that dictates the periodicity of the bars used to determine the current and previous levels. For instance, if you specify a periodicity of "Daily", then your previous open will be the open of the previous day, and your current high will be the high of today. If you specify a periodicity of 30 minutes, then your previous low will be the low of the previous 30 minute bar, while your current open will be the open of the current 30 minute bar. Each horizontal reference line is labeled with a description and value. (e.g. 33.75 PrevOp) This option also comes with an additional color, allowing the user to specify a different color for current versus previous lines.
Above is a 10-minute chart of the Microsoft (MSFT). The BarLines are drawn as horizontal reference lines in red and blue. The blue lines represent the High, Low, and Open of the previous day, while the red lines represent the High, Low, and Open of the current day.