Can I wire a dimmer in series with another dimmer?
No, this really won't work.  Suppose you have 2 dimmers at 20% and 50%.   You are hoping the effect will be multiplicative, that is, 50% of 20% is 10%.  It won't.  

Two SCR dimmers in series will, at best, give you the lower dimming level of the two, i.e. 20%. 

A PWM dimmer, commonly used on dedicated LED circuits, pulses at its own high frequency. If you have two of them, they will pulse at different frequencies.  This will create a much lower "beat frequency", in music this is what makes it annoying when instruments are out of tune with each other.  In light, this would look like pulsing or shimmering.  You won't like it.  

Actual LED emitters can be dimmed very effectively to absolutely any light level. Turn the LED on for 10 microseconds and off for 990 microseconds, you will get 1% brightness - they can be controlled that precisely.   It's a lot harder in built commercial products, which have to work with a variety of existing dimmer technologies made for incandescents, and also hit a "price point" that will make you snatch it off the shelf at Home Depot.  The result of these compromises is lousy dimming range.