ScriptableRenderPipeline/com.unity.shadergraph/Editor/Resources/Styles/Controls/Texture3DSlotControlView.uss

Texture3DSlotControlView {
    flex-direction: row;
    align-items: center;
}

Texture3DSlotControlView > ObjectField {
    margin-top: 0;
    margin-bottom: 0;
    margin-left: 0;
    margin-right: 0;
    width: 100;
}