Finding a particular routine that you want to debug is very simple, just press Ctrl+F. This will bring up the Find Routine window. Simply type in the routine you want to find and it will be displayed. The 'Find Routine' window actually performs a wildcard match for all routines which contain the text you typed, so you could just type the first few characters. For example if the routine required was called 'GET_SATURATED_RATIO' then typing in 'GET_SATUR' will probably find it. If there is more than one routine that matches your text then a list will be displayed.
In addition to pressing Ctrl+F you can also select Find Routine from the Tools menu or use the Find command from the debugger command line.