COHEADER_EXT is a standard SAP Structure so does not store data like a database table does. It can be used to define the fields of other actual tables or to process "Document Header for Screens in Manual Actual Postings (Ext.)" Information within sap ABAP programs. This is done by declaring abap internal tables, work areas or database tables based on this Structure. These can then be used to store and process the required data appropriately. i.e. DATA: wa_COHEADER_EXT TYPE COHEADER_EXT.
The COHEADER_EXT table consists of various fields, each holding specific information or linking keys about Document Header for Screens in Manual Actual Postings (Ext.) data available in SAP. These include VAL_GJAHR (Valuation Year)... See below for full list along with technical details, documentation, text table, check tables, foreign key relationships, conversion routines, relevant tcodes and example ABAP select code etc. .