Mark tones by horizontal lines in spectrogram

Setup: Audacity 2.3.2 on ArchLinux.

I’m working on a snippet of clean sound and look for ways to mark “tones” on spectrogram.
I see spectrogram has EAC mode to roughly grasp the tone.
However, it would be better if I can plot an horizontal line on specific frequency.
It would be more specific and visually convenient.
Does Audacity provides this kind of functionality?

Audacity does not provide horizontal guide lines on the spectrum, but if you enable “Advanced vertical zooming” then you can easily zoom in vertically for any frequency range that you are interested in. See:

Note that while dragging the mouse on the vertical ruler (with “Advanced vertical zooming” enabled), horizontal guide lines appear across the track. This can be used as a temporary guide line - then press “Esc” (before releasing the mouse key) to cancel the zoom.

Thanks. That somewhat helps me a bit.