The "callback hell" example is a rather tame one, since the code is readable in a single location just with some nesting. So when I see the FRP solution which is the same amount of code I'm not certain that in a complex example this actually solves the problem. You can still have lift statements scattered around a program just like you can have callbacks to various functions scattered around.

The solution to GOTO was to remove it and replace it with a few control structure forms that enforced locality. I remember converting someone's GOTO-laced code once and basically everything could be re-written with some clever use of do-while with break statements and an occasional flag variable. do-while, while, for, etc. replace GOTO in 99% of cases and enforce the desired code locality for readability.

So what syntactical structure could enforce locality of time-connected variables?

E.g. some idea like this:

    data, err <- $.ajax(requestUrl1)
    if( err ) {
      console.log(err)
      return
    }
    data2, err <- $.ajax(makeRequestUrl2(data))

Where the <- syntax could be like an = statement but say that the assignment and all following statements are placed in a callback.