If you develop an extension and then you even though your "Apply a set of extended fields" in the FE plugin have indicated, one or more fields missing, they can upgrade easily solve this: Open the
ext_tables.php (in your extension directory).
addiction now following code: :: addTCAcolumns ("tt_content", $ tempColumns, 1);
now just add this line:
$ TCA ['tt_content'] ['types'] ['list'] ['subtypes_addlist']
[$ _EXTKEY '_pi1'.] = 'tx_smartimggal_categories';
said to be 'tx_smartimggal_categories' replaced by the field must be created by you. If you have multiple fields, you can simply remove the commas.