you can connect one part to another and then move it away with fine tuner

@Goldenbullet555 Use a glass fuselage with high health and zero opacity then. Or just separate the two planes and use parts connection to make a non-physical link between them that still works even if they aren't visibly connected

@ShinyGemsBro No, I want the part to be there during flight, however I don't want to see it

Simulator?
If you mean the designer, and you're on PC, you can select the part and press H to hide the parts you temporarily don't want to see.
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Otherwise if you mean to fully remove the part you want to see, just physically trash it like any other part you have no function for.