There is only one range for current measurement, which goes up to 10 amps with about 5 microamp resolution. Some milli amps would be more realistic, as test leads pick up noise and couple last digits are basically random anyhow.
I would suggest using external shunt resistor for extremely small currents, but it would mean that you need to do way more mental conversions on the fly, this time from (milli)volts and probably with stranger ratio.
And again, free math channel would help, but unfortunately it is not (yet?) implemented.