[FEATURE] Deeper type-ahead in builder

**Is your feature request related to a problem? Please describe.**
I spend a lot of time getting down into multiple levels of variables. For example, I have a Config step at the beginning that holds a lot of the things that need to be plugged in repeatedly elsewhere in later steps, such as the schema for my landing zone in Snowflake: {{steps.Config.$return_value.snowflake_lz_schema}}.

**Describe the solution you'd like**
It is a start that I can generally type: `st, tab, Co, tab, tab, lz, down-arrow, tab` for example (there's only ever one value after I pick the step name. It would be really cool if I could type 'lz' and it would go through all of the past steps, the environment, etc (if there is anything else to fit into 'etc') and show me the things in that list. In this case, it would probably show:

- steps.Config.$return_value.snowflake_lz
- steps.Config.$return_value.snowflake_lz_schema

**Do you have a workaround?**
Yes, I can type the beginning of the name of each level, as described above

**Comparable features in other tools?**
No idea.

**Additional context**
Just trying to save some more time on the implementation work.