Final answer:
The Pencil tool in Pro Tools is enabled only when zoomed in to the sample level, allowing for precise manual waveform editing.
Step-by-step explanation:
The Pro Tools edit tool that is only enabled when the edit window view is zoomed in to the sample level is the Pencil tool. This tool allows for precise editing of individual audio samples, making it possible to draw in waveforms manually. This level of detail is necessary when correcting clicks, pops, or other audio artifacts that are only visible at the sample level. The Pencil tool is typically disabled at higher zoom levels because editing single samples is generally not practical or necessary when viewing larger sections of audio.