$migxCfg = $modx->newObject('migxConfig');
$migxCfg->fromArray(array(
'name' => 'ConfigTest',
'formtabs' => '[{"MIGX_id":1,"caption":"Neuer Slide","print_before_tabs":"0","fields":[{"MIGX_id":1,"field":"slideTitle","caption":"Titel","description":"","description_is_code":"0","inputTV":"","inputTVtype":"","validation":"","configs":"","restrictive_condition":"","display":"","sourceFrom":"config","sources":"","inputOptionValues":"","default":"","useDefaultIfEmpty":"0","pos":1},{"MIGX_id":2,"field":"slideText","caption":"Text","description":"","description_is_code":"0","inputTV":"","inputTVtype":"text","validation":"","configs":"","restrictive_condition":"","display":"","sourceFrom":"config","sources":"","inputOptionValues":"","default":"","useDefaultIfEmpty":"0","pos":2},{"MIGX_id":3,"field":"slideImage","caption":"Bild","description":"","description_is_code":"0","inputTV":"","inputTVtype":"image","validation":"","configs":"","restrictive_condition":"","display":"","sourceFrom":"config","sources":"[{\"MIGX_id\":1,\"context\":\"web\",\"sourceid\":2}]","inputOptionValues":"","default":"","useDefaultIfEmpty":"0","pos":3}],"pos":1}]',
'extended' => '{"migx_add":"Neuer Slide","disable_add_item":"","add_items_directly":"","formcaption":"","update_win_title":"Neuen Slide einstellen","win_id":"","maxRecords":5,"addNewItemAt":"bottom","multiple_formtabs":"","multiple_formtabs_label":"","multiple_formtabs_field":"","multiple_formtabs_optionstext":"","multiple_formtabs_optionsvalue":"","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":"","hooksnippets":"","cmpmaincaption":"","cmptabcaption":"","cmptabdescription":"","cmptabcontroller":"","winbuttons":"","onsubmitsuccess":"","submitparams":""}',
'columns' => '[{"MIGX_id":1,"header":"Titel","dataIndex":"slideTitle","width":150,"sortable":"false","show_in_grid":1,"customrenderer":"","renderer":"","clickaction":"","selectorconfig":"","renderchunktpl":"","renderoptions":"","editor":""},{"MIGX_id":2,"header":"Text","dataIndex":"slideText","width":200,"sortable":"false","show_in_grid":1,"customrenderer":"","renderer":"","clickaction":"","selectorconfig":"","renderchunktpl":"","renderoptions":"","editor":""},{"MIGX_id":3,"header":"Bild","dataIndex":"slideImage","width":"","sortable":"false","show_in_grid":1,"customrenderer":"","renderer":"this.renderImage","clickaction":"","selectorconfig":"","renderchunktpl":"","renderoptions":"","editor":""}]',
'contextmenus' => 'update||duplicate||remove||movetotop_migx||movetotop_bottom',
), '', true, true);
$migxCfg->save();
This question has been answered by Bruno17. See the first response.
yourconfig:yourpackage
you don't need to import configs, you can just add the packagename to the configname like:
yourconfig:yourpackage
this does read the config from file instaed from db.

$tvs[$i]= $modx->newObject('modTemplateVar');
$tvs[$i]->fromArray(array(
'id' => $i,
'name' => 'slideshow',
'caption' => 'Slideshow',
'description' => 'MIGx Slideshow Template-Variable',
'type' => 'migx',
'display' => 'default',
'locked' => 0,
'rank' => 0,
'default_text' => '',
'input_properties' => 'a:7:{s:7:"configs";s:23:"configName:packageName";s:8:"formtabs";s:0:"";s:7:"columns";s:0:"";s:7:"btntext";s:0:"";s:10:"previewurl";s:0:"";s:10:"jsonvarkey";s:0:"";s:19:"autoResourceFolders";s:5:"false";}',
),'',true,true); $i++;