Lowering and raising trust?
I don't remember the specifics, but it depends on how you use the items. Trust-raising/lowering item A, for example, raises the trust of character W greatly, raises the trust of character X slightly, lowers the trust of character Y slightly, and lowers the trust of character Z greatly. So basically, if an item can be used to raise the trust of a party member, it can also be used to lower the trust of another party member (it depends on the specific item which character will be affected in which way). By using this method, you can regulate your party members' trust (and you can even temporarily put Celine's dolls back so that her ending priority doesn't interfere with your plans).
Here is an incomplete list of trust items. My old notes can be cryptic, and have errors.
Item
Location
Character
lunar armor
northwest izar port
duo guard jewel x2
north of Mt Hoba
Nadia
duo attack jewel
sallus ruins
duo magic jewel
sallus ruins
thief jewel
sallus ruins
country baton+24
sallus ruins
lunar sacle
island south of arnot temple
negate jewel
sirona port
trust jewel
sirona port
elemental jewel a
nowarl city
lunar dress x3
island north of nowarl city
void jewel
kyle village
uriel
experience bag x4
kyle village
uriel
vit+16 jewel
kyle village
uriel
mind jewel
Mt. Moiray
nadia
miracle jewel>
hollah ruins
stella
shining lizard jewel
hollah ruins
stella
experience bag
hollah ruins
uriel
ability seed
yolkai hollow
stella
marsh wyvern jewel
yolkai hollow
stella
wyvern jewel x2
wakkami forest
nadia
seaweed quartz
map nw of arnolt temple
nadia
hp+16 jewel x2
map se of nowarl
nadia
Item
Location
Character
lunar armor
northwest izar port
duo guard jewel x2
north of Mt Hoba
Nadia
duo attack jewel
sallus ruins
duo magic jewel
sallus ruins
thief jewel
sallus ruins
country baton+24
sallus ruins
lunar sacle
island south of arnot temple
negate jewel
sirona port
trust jewel
sirona port
elemental jewel a
nowarl city
lunar dress x3
island north of nowarl city
void jewel
kyle village
uriel
experience bag x4
kyle village
uriel
vit+16 jewel
kyle village
uriel
mind jewel
Mt. Moiray
nadia
miracle jewel>
hollah ruins
stella
shining lizard jewel
hollah ruins
stella
experience bag
hollah ruins
uriel
ability seed
yolkai hollow
stella
marsh wyvern jewel
yolkai hollow
stella
wyvern jewel x2
wakkami forest
nadia
seaweed quartz
map nw of arnolt temple
nadia
hp+16 jewel x2
map se of nowarl
nadia
Older, but not wiser