Add lines via plugin

Dear community,

I'm currently struggling with adding simple black lines via plugin. Already the first step to create an element of type LINE

var line = newElement(Element.LINE);

returns an error: cannot create type 8

Any ideas on how to successfully create a line object and define start and end point of the line?

Maybe it's possible with TEXTLINE? Do I have to assign the object to a note or a segment or the cursor (cursor.add)?

This is not the first element I have troubles to create objects and assign them to the score. Adding a Figured Bass item to the score via plugin creates "something" but this thing has not the properties of a real figured bass inserted with CTRL + G. Tried this as a workaround for simple lines.

Only trying to create lines via plugin. Kind of helpless...

Best regards,
Stoffl