Conditions generally cannot detect “change” per se. So there is no condition for Window Changed, or Application Changed, or Clipboard Changed, or whatever. It might well be useful if there was some way, but that is not how conditions work since conditions are used in various places other than Pause Until (like If) and what would it mean to say “If Window Changed” - changed from when? Maybe for the looping actions it might be possible to add some sort of change condition.
@JMichaelTX is the best solution for this, just detect the WINDOWCOUNT() increasing.
But generally if you want to detect a change you need to use a trigger to do it. So you have a macro that detects the change and sets a variable. And your macro clears the variable, enables the macro, pauses until the variable becomes set, disables the macro and continues. This is a little cumbersome, but is a general way of handling “changes” as opposed to “state”.