How can I cycle through 4 LEDs with Timer Off Function (TOF)?
Your code looks wrong to me at first look. The timers have to be called each scan, the best way is to put them in the bottom of your code.
TON(&amp;TON1);
TON(&amp;TON2);
TOF(&amp;TON3);
TOF(&amp;TON4);
TOF(&amp;TON4);
....

Then you have to assign the state in .IN value. You can do it also in if..then if you want, the imortant thing is that they are always defined true or false.
IF TON2.IN == 1 THEN

This is not valid, .IN is input to timer, you have to define it like TON2.IN = true /or/ false, it's not an integer value, rather boolean.
  IF TON2.Q THEN         
    QB_SET (led_linear_sensor_alarm, 1);
    TON3.IN = 1;

This is simply:
  IF TON2.Q THEN         
    QB_SET (led_linear_sensor_alarm, 1);
    .....

and
TON3.IN := TON2.Q;

A bottom of your program should be something like this, then you may use .Q values to set your outputs accordingly.
TON1.IN := not TON5.Q;
TON2.IN := TON1.Q;
TON3.IN := TON2.Q;
TON5.IN := TON4.Q;

TON(&amp;TON1);
TON(&amp;TON2);
TON(&amp;TON3);
TON(&amp;TON4);
TON(&amp;TON4);
    ....