I could provide a solution to this introducing a new key field which gives the index field names and order of the mm table.
$TCA['tx_extensionname_tables_mm'] = Array (
'ctrl' => Array (
'title' => 'LLL:EXT:extensionname/locallang_db.php:tx_extensionname_tables_mm', ## WOP:[tables]1[title]
'label' => 'title', ## WOP:[tables]1[header_field]
'tstamp' => 'tstamp',
'crdate' => 'crdate',
'cruser_id' => 'cruser_id',
'key' => 'uid_local,uid_foreign',
'sortby' => 'sorting', ## WOP:[tables]1[sorting]
'delete' => 'deleted', ## WOP:[tables]1[add_deleted]
'enablecolumns' => Array ( ## WOP:[tables]1[add_hidden] / [tables]1[add_starttime] / [tables]1[add_endtime] / [tables]1[add_access]
'disabled' => 'hidden', ## WOP:[tables]1[add_hidden]
'starttime' => 'starttime', ## WOP:[tables]1[add_starttime]
'endtime' => 'endtime', ## WOP:[tables]1[add_endtime]
'fe_group' => 'fe_group', ## WOP:[tables]1[add_access]
),
'dynamicConfigFile' => t3lib_extMgm::extPath($_EXTKEY).'tca.php',
'iconfile' => t3lib_extMgm::extRelPath($_EXTKEY).'icon_tx_extensionname_tables.gif',
),
'feInterface' => Array (
'fe_admin_fieldList' => 'hidden, starttime, endtime, fe_group, min_size_id, max_size_id, additional mediumtext',
)
);
A concept like this is needed anyways to make mm tables editable in the backend and independant from the field names 'uid_local' and 'uid_foreign'.
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