Is there a way to set a rule to only pick up 2 slot leggings? I selected 'LowerLegs' and 'UpperLegs' in the armor coverage section, but it is picking up pieces of armor that meets the rule needs and covers either of the slots, and not both. Any advice?

Look at all the available armor sets and look at the names for pieces that cover upper/lower legs.

Hopefully most of the names share a common word. Then add that word to the name must contain field.

For example, to pick up pieces of armor that only cover the lower arm, you select lower arm in the armor section. But then you'll pick up full coats. Add brace to the Name must contain field, and now you only get lower arm pieces.

I want the opposite to occur actually. I'm trying to pick up low burden leggings to wear with a hauberk. I've set it to pick up lower and upper legs with burden under 1000 and armor level above 230. I only want legs covering both slots, but it picks up tassets, etc as well.

Come to think of it, I may be able to use this in reverse. I 'believe' all 2 slot legs have "Leggings" in the name, so I'll try that.

Yes, you need to use the method I described and adapt it to YOUR requirements.

Use the wiki and see what all the upper/lower leg pieces are called over all the armor types.

Not all two slot leggings have "leggings" in the name. I believe "pants" are two slot as well, though I might be misremembering.