I can't see any way to have the QGIS decorations that are available to the desktop passed on to any outputs! The don't show up in layouts. They don't export to html via QGIS2web. (except the scalebar!) What was the idea of having them available only to the desktop and not be able to be printed or displayed anywhere else? Am I missing something?
Answer for QGIS2WEB (leaflet): For decoration "title label" and "copyright label" you could use:
Project properties - metadata: title and abstract. You can also use html for this fields.
Within qgis2web you should:
- appearance - add abstract: choose the edge to show the abstract text
- appearance - template: choose full-screen
These are the fast possibilities. Furthermore you can edit the index.html file after leaflet export.