Hidden notes

Disallow adding child notes

To enforce at server level go to services/notes.ts and look for the getAndValidateParent method. Look for the params.ignoreForbiddenParents if statement and add it there.
To hide the plus button in the note tree, go to widgets/note_tree in the client and look for enhanceTitle. Look for the if statement which starts with !["search", "launcher"].includes(note.type).
To disable it from the contextual menu, go to tree_context_menu and look for the getMenuItems method. There look for the insertNoteAfter and insertChildNote actions and look at their enabled conditions. If adding a big note type with lots of child notes, see the pattern of optinos & help (rename and augment the notOptionsOrHelp variable.