Ubuntu by default comes with the bash shell. Bash is great but I personally find it harder to customize. That is why I use Z shell, more commonly known as zsh. To manage my zsh configuration, I use Oh My Zsh. It has a huge community and makes it trivial to install and use plugins. - Source: dev.to / almost 2 years ago

The reason you don’t see a feature like blocks (with the exception of Upterm) in most other terminals is because the terminal has no concept of what program is running, or really of anything that’s happening within the shell. At a high level, a terminal reads and writes bytes from a pseudoterminal to interact with the shell. This technology is very antiquated--the shell essentially thinks it is interacting with a... - Source: dev.to / about 2 years ago

Suprised that no one has mentioned this, but upterm seems to be exactly what you're describing--a terminal emulator that shows a drop-down list of suggestions with explanations. Sadly, only a few commands are supported, and it's no longer being worked on. Source: over 2 years ago

Currently haven't gone as far as making some kind of dedicated shell component though. I find it important that normal shells can work fine with in Extraterm. There was a project from a few years back which also mashed GUI/emulator together with the shell side, Upterm. SSH and containers tend to be the natural enemy of having your own shell though. Source: over 3 years ago