One of the optimizations, which is related to breakpoints, can be disabled with a new attribute named #DebuggerDisableOptimizations (it is enabled by default).
I will use this code to explain why you may want to disable it:
Sub Timer1_Tick
S1
Log("After S1")
End Sub
Sub S1
Log("abc") 'put a breakpoint here
Log("def") 'this line will be paused
End Sub
If you put a breakpoint on the line and then press F8 (step) twice the program will continue and will not pause on the "After S1" line.
If the optimization is disabled then it will pause on that line. However the code execution will be slower. You can see it with current versions of B4A, i or J where a single breakpoint can make the whole program much slower. This optimization dramatically improves it.