Sticky Problems with posting here at k.org

That is incomprehensible to me. My "ckeditor.js" has the same size as yours (695. 045) and at the end of the file it also says :936,auto,removeformat,960,auto,selectall,984,auto,source-rtl,1008,auto,source,1032,auto,scayt,1056,auto,redo-rtl,1080,auto,redo,1104,auto,undo-rtl,1128,auto,undo,1152,auto','icons. png');})();CKEDITOR.lang.languages={"nl":1};}());
But the "nl" does not cause any problems.
There should be something else.

I'm getting a little confused
in your solution you are talking about " I have copied the ckeditor_config.js to customckeditor_config.js and there between config.smilie_discriptions=""; and config.toolbarGroups = [
the line config.defaultLanguage = 'de'; inserted." and that doesn't work here locally.
And in your last answer you talk about "ckeditor.js"
and as the ckeditor.js modification in my video on the test site says it works well both live and locally.
Can you post an image of your modification here?

Der erste Teil meiner customckeditor_config.js

/**
 * @license Copyright (c) 2003-2021, CKSource - Frederico Knabben. Alle Rechte vorbehalten.
 * Für die Lizenzierung, siehe ckeditor.com/legal/ckeditor-oss-license
 */

CKEDITOR.editorConfig = function( config ) {
    // Definieren Sie hier Änderungen an der Standardkonfiguration. Zum Beispiel:
    // config.language = 'fr';
    // config.uiColor = '#AADC6E';
    // config.skin = 'moono-lisa';
    
    config.smiley_descriptions="";

    config.defaultLanguage = 'de';

    config.toolbarGroups = [
        { name: 'document', groups: [ 'mode', 'document', 'doctools' ] },
        { name: 'clipboard', groups: [ 'clipboard', 'undo' ] },
        { name: 'editing', groups: [ 'find', 'selection', 'spellchecker', 'editing' ] },
        { name: 'forms', groups: [ 'forms' ] },
        { name: 'basicstyles', groups: [ 'basicstyles', 'cleanup' ] },
        { name: 'paragraph', groups: [ 'list', 'indent', 'blocks', 'align', 'bidi', 'paragraph' ] },
        { name: 'links', groups: [ 'links' ] },
        { name: 'insert', groups: [ 'insert' ] },
        { name: 'social', groups: [ 'social' ] },
        { name: 'styles', groups: [ 'styles' ] },
        { name: 'colors', groups: [ 'colors' ] },
        { name: 'tools', groups: [ 'tools' ] },
        { name: 'andere', gruppen: [ 'andere' ] },
        { name: 'about', groups: [ 'about' ] }
    ];

Der Eintrag in der Aurelia-Vorlage BBCode spalte:
 

thanks,
that's how I did it
but i will go here all over again
download latest Joomla and kunena and create test site

another step further in clean installation, the custom solution does not work
but if i put in the "ckeditor_config.js" there "config.language = 'en';
" does it work
if i config.language = 'nl'; then it won't work
also tested with plugins System - Language Code and System - Language Filter
on or off makes no difference.
Only when I turn on the System - Language filter disappears above the kunena navbar

Does it also work here on the Kunena.org forum or only on the test site?

Gindi