I made an assembly of several parts but in the parts tree I don't have a + in front of the name of the parts which, when clicked on it, displays the sketches and extrusions of the part.
This is a problem for me because I started to create a part in the assembly and I left the sketch of this part without wanting to and I can't go back to it.
Are you in graphic representation? If so, it's normal, you have to take the presentation in Master's degree
OR
Just above the creation tree there is a drop-down menu it seems to me where you have to check in "Tree filters" the "features" option (Sorry I don't have Creo at home but only Pro-E! I'll be happy Tuesday on Creo)
EDIT: So that's it I checked, there is a drop-down menu above the creation tree (see image)