You can add scaling to your products through a convenient user interface.
Just add a Bone Scale from the Inspector panel, select which bone you would like to scale, and choose how much to scale on each axis.
These Axis are local to each bone, so the Z is always referencing the direction the bone is facing
For example, to make a longer arm, you could scale up lfBicep in the Z direction.
Keep in mind that if you scale a bone, the scaling propagates down the rest of the bones in front of it, so you may have stretched out body parts you weren’t expecting. You can account for this by scaling bones down the chain in the Z axis by the reverse of what you scaled the first bone.
So if you scale lfBicep in the Z by 2, you should scale lfHand in the Z by .5 so the hand is the correct scale, but the arm is stretched out.