diff --git a/databuilder/README.md b/databuilder/README.md
index 416148fdf7..90bfbd73ae 100644
--- a/databuilder/README.md
+++ b/databuilder/README.md
@@ -1700,6 +1700,28 @@ Adds the same set of tags to all tables produced by the job.
 #### [GenericTransformer](./databuilder/transformer/generic_transformer.py)
 Transforms dictionary based on callback function that user provides.
 
+#### [ComplexTypeTransformer](./databuilder/transformer/complex_type_transformer.py)
+Transforms complex types for columns in a table by using a configured parsing function. The transformer takes a `TableMetadata` object and iterates over its list of `ColumnMetadata` objects. The configured parser takes each column as input and sets the column's `type_metadata` field with the parsed results contained in a `TypeMetadata` object.
+
+**If you use Hive as a data store:**<br>
+Configure this transformer with the [Hive parser](./databuilder/utils/hive_complex_type_parser.py).
+
+**If you do not use Hive as a data store:**<br>
+You will need to write a custom parsing function for transforming column type strings into nested `TypeMetadata` objects. You are free to use the [Hive parser](./databuilder/utils/hive_complex_type_parser.py) as a starting point. You can also look online to try to find either a grammar or some OSS prior art, as writing a parser from scratch can get a little involved. We strongly recommend leveraging PyParsing instead of regex, etc.
+
+New parsing functions should take the following arguments:
+- Column type string
+- Column name
+- `ColumnMetadata` object itself
+
+Within the parsing function, [TypeMetadata](./databuilder/models/type_metadata.py) objects should be created by passing its name, parent object, and type string.
+
+**Things to know about [TypeMetadata](./databuilder/models/type_metadata.py)**<br>
+- If the existing subclasses do not cover all the required complex types, the base class can be extended to create any new ones that are needed.
+- Each new subclass should implement a `is_terminal_type` function, which allows the node and relation iterators to check whether to continue creating the next nested level or to stop due to reaching a terminal node.
+- `ScalarTypeMetadata` is the default type class that represents a terminal state. This should be used to set any column's `type_metadata` when it is not a complex type, or for the innermost terminal state for any complex type. Having all the columns set the `type_metadata` field allows the frontend to know to use the correct nested column display.
+- Subclasses should set a `kind` field that specifies what kind of complex type they are. This is used by the frontend for specific type handling. For example, for arrays and maps a smaller row is inserted in the display table to differentiate them from named nested columns such as structs.
+
 ## List of loader
 #### [FsNeo4jCSVLoader](https://github.com/amundsen-io/amundsen/blob/main/databuilder/databuilder/loader/file_system_neo4j_csv_loader.py "FsNeo4jCSVLoader")
 Write node and relationship CSV file(s) that can be consumed by Neo4jCsvPublisher. It assumes that the record it consumes is instance of Neo4jCsvSerializable.
diff --git a/frontend/amundsen_application/static/js/ducks/tableMetadata/api/helpers.ts b/frontend/amundsen_application/static/js/ducks/tableMetadata/api/helpers.ts
index cb2a6e3bb3..ecb5d3f955 100644
--- a/frontend/amundsen_application/static/js/ducks/tableMetadata/api/helpers.ts
+++ b/frontend/amundsen_application/static/js/ducks/tableMetadata/api/helpers.ts
@@ -54,7 +54,7 @@ export function processColumns(
       ...column,
       key: tableKey + '/' + column.name,
       children:
-        nestedType && isNestedColumnsEnabled()
+        !column.type_metadata && nestedType && isNestedColumnsEnabled()
           ? convertNestedTypeToColumns(nestedType)
           : undefined,
     };
diff --git a/frontend/amundsen_application/static/js/features/ColumnList/index.tsx b/frontend/amundsen_application/static/js/features/ColumnList/index.tsx
index dde0246ac0..c9b934e20d 100644
--- a/frontend/amundsen_application/static/js/features/ColumnList/index.tsx
+++ b/frontend/amundsen_application/static/js/features/ColumnList/index.tsx
@@ -173,7 +173,8 @@ const ColumnList: React.FC<ColumnListProps> = ({
       key: item.key,
       name: item.name,
       isEditable: item.is_editable,
-      isExpandable: false,
+      isExpandable:
+        item.type_metadata && item.type_metadata.children.length > 0,
       editText: editText || null,
       editUrl: editUrl || null,
       tableParams,
diff --git a/frontend/amundsen_application/static/js/pages/TableDetailPage/index.tsx b/frontend/amundsen_application/static/js/pages/TableDetailPage/index.tsx
index 542d32833a..fe43038e95 100644
--- a/frontend/amundsen_application/static/js/pages/TableDetailPage/index.tsx
+++ b/frontend/amundsen_application/static/js/pages/TableDetailPage/index.tsx
@@ -353,12 +353,10 @@ export class TableDetail extends React.Component<
     });
   };
 
-  hasColumnsToExpand = () =>
-    // TODO use this instead once the new nested columns display is turned on
-    // const { tableData } = this.props;
-    // return tableData.columns.some((col) => col.type_metadata?.children?.length);
-
-    false;
+  hasColumnsToExpand = () => {
+    const { tableData } = this.props;
+    return tableData.columns.some((col) => col.type_metadata?.children?.length);
+  };
 
   renderTabs(editText, editUrl) {
     const tabInfo: TabInfo[] = [];
diff --git a/frontend/setup.py b/frontend/setup.py
index 3afad6a370..d51d4cba5a 100644
--- a/frontend/setup.py
+++ b/frontend/setup.py
@@ -45,7 +45,7 @@ def build_js() -> None:
 with open(requirements_path) as requirements_file:
     requirements_dev = requirements_file.readlines()
 
-__version__ = '4.1.2'
+__version__ = '4.2.0'
 
 jira = ['jira==3.0.1']
 asana = ['asana==0.10.3']