This question has been answered by Bruno17. See the first response.
{
"formtabs":[
{
"MIGX_id":1,
"caption":"Elearningpagina's",
"print_before_tabs":"0",
"fields":[
{
"MIGX_id":2,
"field":"elearningpage",
"caption":"E-learning pagina",
"description":"Welke pagina moet worden toegevoegd",
"description_is_code":"0",
"inputTV":"",
"inputTVtype":"listbox",
"validation":"",
"configs":"",
"restrictive_condition":"",
"display":"",
"sourceFrom":"config",
"sources":"",
"inputOptionValues":"@EVAL return $modx->runSnippet('getResources', array('parents'=>'3', 'showUnpublished'=>'1', 'showHidden'=>'1', 'hideContainers'=>'1','tpl'=>'TVlist','tplLast'=>'TVListLast','context'=>'web', 'limit'=>'0', 'sortby'=>'pagetitle','sortdir'=>'ASC'));",
"default":"",
"pos":1
}
],
"pos":1
}
],
"contextmenus":"",
"actionbuttons":"",
"columnbuttons":"",
"filters":"",
"extended":{
"migx_add":"Voeg pagina's toe",
"disable_add_item":"",
"formcaption":"E-learnings pagina's",
"update_win_title":"E-learnings pagina's",
"win_id":"migx_elearning",
"maxRecords":"",
"addNewItemAt":"bottom",
"multiple_formtabs":"",
"actionbuttonsperrow":4,
"winbuttonslist":"",
"extrahandlers":"",
"filtersperrow":4,
"packageName":"",
"classname":"",
"task":"",
"getlistsort":"",
"getlistsortdir":"",
"sortconfig":"",
"gridpagesize":"",
"use_custom_prefix":"0",
"prefix":"",
"grid":"",
"gridload_mode":1,
"check_resid":1,
"check_resid_TV":"",
"join_alias":"",
"has_jointable":"yes",
"getlistwhere":"",
"joins":"",
"cmpmaincaption":"",
"cmptabcaption":"",
"cmptabdescription":"",
"cmptabcontroller":"",
"winbuttons":"",
"onsubmitsuccess":"",
"submitparams":""
},
"columns":[
{
"MIGX_id":3,
"header":"E-learning page",
"dataIndex":"elearningpage",
"width":"",
"sortable":"false",
"show_in_grid":"0",
"renderer":"",
"clickaction":"",
"selectorconfig":"",
"renderchunktpl":"",
"renderoptions":""
},
{
"MIGX_id":1,
"header":"E-learning pagina",
"dataIndex":"elearning-pagetitle",
"width":"",
"sortable":"false",
"show_in_grid":1,
"renderer":"this.renderChunk",
"clickaction":"",
"selectorconfig":"",
"renderchunktpl":"[[#[[+elearningpage]].pagetitle]] (id [[+elearningpage]])",
"renderoptions":""
}
]
}