Yes. Two polarizing elements can act as a variable light reducer: rotate one relative to the other and the transmission changes from fairly bright to much darker. In practice, variable ND filters are based on this idea.

Setup is simple in principle: stack two polarizing filters and rotate one. However, there are tradeoffs:

• It is not perfectly neutral, so color casts can appear.
• Image quality can drop because you’re adding more glass.
• At stronger settings, uneven darkening or other artifacts may appear, especially with wide lenses.
• Metering/autofocus can become less reliable as the view gets very dark.

Light reduction is variable rather than fixed. The exact range depends on the filters used and their orientation, but it can span from modest reduction to several stops. It will not usually reach perfect blackout, and the darkest setting may also be the least clean optically.

So: yes, it works, but it’s a compromise. It can be useful for experimentation, but a purpose-made variable ND is usually more predictable and convenient.