I’m using the following code provided by Reinmar here to create multiple instances of CKEditor5. However in Firefox Inspector I get the error: CKEditorError: can't convert null to object

I need to allow <meta> tags in CKEditor5. I wrote a plugin for this, but it doesn’t work with these tags. But it works with another tags e.g. <custommeta>.

CKEditor4 allowed a default configuration to be set in a main configuration file, has this feature been removed in CKEditor5? Must all config options be now set in each instance?

I would like to adjust popup (Ctrl K)

I used CKeditor5 online build tool and included SimpleUploadAdapter. Here is the source of ckeditor.js: