Usage of "the" for possible future objects

Question

I am writing a software user manual so the topic is about possible situations which its users may come across.

Here is an example sentence below:

Enter the window ID which contains an image.

Answer 1

This is a perfectly acceptable sentence. The fact that the window is a hypothetical future window doesn't affect the fact that it is a single, definite window within your discourse, and therefore needs the definite article.

Answer 2

The sentence is fine as is, but a little ambiguous.

It might help if you were more explicit. For example:

Enter the ID of the window which contains an image

Or, if "window ID" is a phrase defined elsewhere in the manual

Enter the window ID of the window containing an image