@redmotion said:

I want to align textures on one component with those on several others (using Texture > position) but when I edit the component all other components turn grey/untextured.
Is there any way to have textures display on everything while editing one component?

No, I don't think SU ever displayes texture of components in higher levels when you are in editing context of a group or component.

First question could also be interpreted as: .....all other completely differentcomponents with same texture turn grey/untextured.
If so, you need to apply extra geometry (edge or guide) outside editing context by eyeballing, to mark how you do want to make changes to the textures position.
See simple example in attached file:

pre-marked texture position for aligning with neighboring group.