I've made the digit display that Sebastian did, but when I drag the chip into the editor, it doesn't show the display.
That is a feature Sebastian plans to implement in the future:
"In episode 3, displays placed inside of a chip will be visible on the face of that chip when it's used inside of other chips. I still need to figure some stuff out with this feature, but it will be added in a future update." - The itch.io page
it's a feature that is activated in the Code, if your familiar with Unity Development their is an Object called "VideoFeatures", or something, and you can activate that to get the experimental features like seeing the Displays in a chip. Their are some mods, And very helpful posts on how to do this on this forum, so if you can find those you should be able to activate this feature.
https://itch.io/t/3291682/7-segment-displays-in-digital-logic-sim
This should explain everything.