Besides Base Schema, what options do I have to take a pre-built Airtable base and create a visual map/visual workflow to see how everything is connecting, and if a field is a single/multi select, what those options are?
As you see in the screenshot, there is a lot going on, and I would like to get this cleaned up!
I agree that On2Air schemas is the best option. However, it is not the only option.
The first thing I recommend is turning off all the lines in the Base Schema settings except for linked relationships. It may reduce the number of connect lines enough for you to be able to rearrange the tables with no criss-crossing lines.
Another option to consider is my Field List extension with a premium license. It will not give you a visual representation directly. Instead, it creates a table of all the fields in your base. With a premium license and a bit of post-processing, you can see which fields are used to calculate which other fields, and then use filtered views and the Org Chart extension to chained dependencies.