Conditional breakpoints are not set on an executable line of a script but are evaluated during whole script execution.
Select Add Conditional Breakpoint item in main Run menu,
or click on [
] button to add a conditional breakpoint.
Enter the condition you want to be evaluated in dialog box
Add Conditional Breakpoint dialog box :

Also, the new breakpoint appears in the Breakpoints View list.
While the breakpoint is enabled, thread execution suspends after its condition became true. The debugger selects the thread that has suspended and displays the thread's stack frames. The line which set the condition true is highlighted in the editor in the Debug Perspective.
Note :
Conditional breakpoints are different from line breakpoints with condition : first ones are evaluated at each execution line,
while second ones are only evaluated on their definition line execution.