4th edition Basic Set lists all cover modifiers on B407/B408 - extra -2 for shooting through cover and at partially exposed hit locations.
Firing through an occupied hex penalty (B389) stays the same, at -4 for each person.
Tactical Shooting (TS28) has an optional rule that adds more granular modifiers depending on the size and type of cover, from -1 to -4.
EDIT: Went through other modifiers:
Some general Active Defense modifiers are described as being exclusive to Dodge (B374, B390, B391):
Shield DB
attacked from side (applies to all defences)
attacked from rear (disallows any defences without specific advantages, and then applies extra -2 only ot parry)
Some hit locations are missing a "[*hit torso]" note (B552, note [1])
Eyes (also missing [front/sides only])
Skull
Face
Groin
Neck
Vitals
(B552, notes [2], [11])
Vitals should have [imp, pi, or tight-beam burning only] (sadly no official abbreviation, but I guess tbb could work)
Eyes should have the same note.
Missing -8 to hit a hand holding a shield (B399)
There are some hit locations added from MA127 (Nose, Jaw, Neck/Limb Vein/Artery), but a few are still missing (Spine, Joints, Ears). Nose and Jaw refer to chest on miss by 1, which is a Low Tech hit location - I'm guessing they're supposed to refer to torso?
Maybe the additional hit locations could be separated into their own subcategory, or tied to an option to make them visible/hidden?
There's also "-5 to hit Vitals, Heart" that I could not find the source for.
4th edition Basic Set lists all cover modifiers on B407/B408 - extra -2 for shooting through cover and at partially exposed hit locations. Firing through an occupied hex penalty (B389) stays the same, at -4 for each person. Tactical Shooting (TS28) has an optional rule that adds more granular modifiers depending on the size and type of cover, from -1 to -4.
EDIT: Went through other modifiers: Some general Active Defense modifiers are described as being exclusive to Dodge (B374, B390, B391):
Some hit locations are missing a "[*hit torso]" note (B552, note [1])
(B552, notes [2], [11]) Vitals should have [imp, pi, or tight-beam burning only] (sadly no official abbreviation, but I guess tbb could work) Eyes should have the same note.
Missing -8 to hit a hand holding a shield (B399)
There are some hit locations added from MA127 (Nose, Jaw, Neck/Limb Vein/Artery), but a few are still missing (Spine, Joints, Ears). Nose and Jaw refer to chest on miss by 1, which is a Low Tech hit location - I'm guessing they're supposed to refer to torso? Maybe the additional hit locations could be separated into their own subcategory, or tied to an option to make them visible/hidden?
There's also "-5 to hit Vitals, Heart" that I could not find the source for.