Almost all of these the game literally tells you about right there in the GUI… When you are building, you get an info bar telling you what button combinations do what. This is smart enough to even depend on what exactly you are building, so it will not tell you about R for build modes when you are building things that don’t have build modes.

Another small thing not everyone knows about: when building normal hyper tubes or pipelines, you can rotate the end point vertically as well. While placing it ( hold left mouse button), you can drag the cursor up/down for elevation, but you can also use the scroll wheel to tilt the connector. This allows for more aesthetic long gradients, without having “steps” on the connectors.