The attribution to Tiny is required by the open source license of TinyMCE. It is possible to turn it off if you are going to place your own attribution somewhere else near the editor in your application, no less prominent
. Or you can purchase a paid license for TinyMCE and then you can just remove it. The rules are here: https://about.tiny.cloud/legal/attribution-requirements/
If you do add your own attribution or buy a license you can remove the Powered By Tiny by adding
branding : false,
To the layout file (*plus\inomads\add-ons\editors\tinymce\layouts) your tinyMCE control is using via the layout property (default is modern). I would recommend creating a copy of the layout file you want to modify and modify the copy and point the tinymce layout property at the new layout. This keeps the original intact and prevents an update from erasing you change.
If your goal is to remove the whole statusbar and not just the Powered By Tiny text on the status bar then you would also add
statusbar : false,
to the layout file.