Hi Jury
your question is already a couple of days old so maybe you already found a solution. If not I think that there might be something missing in the path you are using:
ResourceType.JAVASCRIPT,"text/javascript","/TinyMCEEditorComponent/scripts/tiny_mce/utils/idemodification.js");
I think this should be:
...,"/irj/portalapps/your Project/....."
Best regards
Christophe