This is a continuation of several bugs already addressed by the UF4P:
https://afktrack.afkmods.com/index.php?a=issues&i=26715 (This one has all the details)
https://afktrack.afkmods.com/index.php?a=issues&i=29056
https://afktrack.afkmods.com/index.php?a=issues&i=22482
Muffled limb mods can spawn on both arm and leg pieces, they (in the unfixed state) can however not be attached or crafted to arm armors.
This was fixed by UF4P for Leather, Metal, Combat and Synth mods already, by changing the Target OMOD Keyword on the OMOSs from
ma_armor_XXX_Lining_LimbLeg to ma_armor_XXX_Lining_Limb
The following OMODs are still missing this fix:
mod_armor_RaiderMod_Lining_Limb_ReducedDetection "Muffled" [OMOD:001957D4]
DLC03_mod_armor_Trapper_Lining_Limb_ReducedDetection "Muffled" [OMOD:0300EA6F]
DLC03_mod_armor_Marine_Lining_Limb_ReducedDetection "Muffled" [OMOD:030107C6]
DLC04_mod_armor_Disciples_Lining_Limb_ReducedDetection "Muffled" [OMOD:06026B37]
DLC04_mod_armor_Pack_Lining_Limb_ReducedDetection "Muffled" [OMOD:0602749A]
DLC04_mod_armor_Operators_Lining_Limb_ReducedDetection "Muffled" [OMOD:0602878F]
all of these appear in their respective modcol OMODs for arms (i.e.: The arm armors will spawn with them)
(mod_armor_Universal_Lining_Limb_ReducedDetection "Muffled" [OMOD:001833A1], probably unused)