Adding help text to column headings in a tabular form

There is no out of the box solution for adding help text to column headings in a tabular form. One way is create custom table where you store your help text. Then modify/copy report template and add JavaScript that fetch using Ajax call help text for your column.

In report template I did change Column Heading Template to be:

<th id="#COLUMN_HEADER_NAME#" onmouseover="getColumnHelp(event,this,'#COLUMN_HEADER_NAME#')">#COLUMN_HEADER#</th>

Then I did add to After Rows:

<script type="text/javascript">
function getColumnHelp(pEvent,pThis,pColumn){
  var ajaxRequest = new htmldb_Get(null, $v('pFlowId'), 'APPLICATION_PROCESS=GET_REPORT_HELP', 0);
  ajaxRequest.addParam('x01', pColumn);
  ajaxRequest.addParam('x02', '#REGION_ID#');
  var ajaxResponse = ajaxRequest.get();
  ajaxRequest = null;
  toolTip_enable(pEvent,pThis,ajaxResponse);
}
</script>

And then on demand process GET_REPORT_HELP

DECLARE
  l_help_text VARCHAR2(255);
BEGIN
 
  SELECT help_text
  INTO l_help_text
  FROM DEMO_REPORT_COL_HELP
  WHERE COLUMN_HEADER_NAME = APEX_APPLICATION.G_x01
  AND REGION_ID  = APEX_APPLICATION.G_x02
  ;
 
  htp.prn( REPLACE(REPLACE(l_help_text, chr(10), '\f'), chr(13)) );
 
EXCEPTION WHEN NO_DATA_FOUND THEN
  htp.prn('No help available for this item');
END;

This is my custom help text table DLL:

CREATE TABLE "DEMO_REPORT_COL_HELP" 
   (    "ID" NUMBER NOT NULL ENABLE, 
    "COLUMN_HEADER_NAME" VARCHAR2(30 BYTE) NOT NULL ENABLE, 
    "REGION_ID" VARCHAR2(20 BYTE) NOT NULL ENABLE, 
    "HELP_TEXT" VARCHAR2(255 BYTE), 
    "RESERVED2" VARCHAR2(20 BYTE), 
    "RESERVED3" VARCHAR2(20 BYTE), 
    "RESERVED4" VARCHAR2(20 BYTE), 
    "RESERVED5" VARCHAR2(20 BYTE), 
    "CREATED_ON" DATE NOT NULL ENABLE, 
    "CREATED_BY" VARCHAR2(255 BYTE) NOT NULL ENABLE, 
    "CHANGED_ON" DATE, 
    "CHANGED_BY" VARCHAR2(20 BYTE), 
     CONSTRAINT "DEMO_REPORT_COL_HELP_PK" PRIMARY KEY ("ID"));

And trigger for it:

create or replace TRIGGER "BIU_DEMO_REPORT_COL_HELP" before
  INSERT OR UPDATE ON "DEMO_REPORT_COL_HELP" FOR EACH row 
BEGIN 
 
  IF inserting THEN 
    
    IF :NEW.ID IS NULL THEN 
      SELECT TO_NUMBER(SYS_GUID(), 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX')
      INTO :NEW.ID
      FROM DUAL;
    END IF;
    
    :NEW.CREATED_ON := sysdate;
    :NEW.CREATED_BY := NVL(v('APP_USER'),user);
    :NEW.CHANGED_ON := null;
    :NEW.CHANGED_BY := null;
  END IF;
  IF updating THEN
    :NEW.CHANGED_ON := sysdate;
    :NEW.CHANGED_BY := NVL(v('APP_USER'),user);
  END IF;
  
END;