The one-hot encoder is unselectable. I think this is because the connectors have a very wide selection band around them, meaning the component is completely covered by connector selection areas.
There is a weird work-around - drag select two components, one of which is the real target, then click-drag on the other one that is not obscured by connectors.
The full model shown in the 2nd image illustrates nicely why better control of connector routing would enhance the visual utility of the model.