Escludendo questa cosa dei menu il resto l'ho fatto tramite le impostazioni canoniche e un po' di personalizzazioni della barra unificata.
Ecco il contenuto di xulstore.json
{"chrome://messenger/content/messenger.xhtml":{"task-tree-filtergroup":{"value":"throughcurrent"},"unifinder-search-results-tree-col-title":{"ordinal":"1"},"unifinder-search-results-tree-col-startdate":{"ordinal":"3"},"unifinder-search-results-tree-col-enddate":{"ordinal":"5"},"unifinder-search-results-tree-col-categories":{"ordinal":"7"},"unifinder-search-results-tree-col-location":{"ordinal":"9"},"unifinder-search-results-tree-col-status":{"ordinal":"11"},"unifinder-search-results-tree-col-calendarname":{"ordinal":"13"},"folderTree":{"mode":"all"},"quickFilterBar":{"collapsed":"false"},"today-pane-splitter":{"hidden":"true"},"today-none-box":{"collapsed":"true"},"today-minimonth-box":{"collapsed":"true"},"todo-tab-panel":{"collapsed":"true"},"agenda-panel":{"collapsed":"true","collapsedinmodes":"calendar"},"mini-day-box":{"collapsed":"true"},"messagepaneboxwrapper":{"collapsed":"false","height":"230"},"messengerWindow":{"screenX":"98","screenY":"0","width":"1291","height":"816","sizemode":"maximized"},"spacesToolbar":{"hidden":"true"},"calendar-task-tree":{"widths":"8 8 8 8 8 8 8 8 8 8 8 8","ordinals":"1 3 5 7 9 11 13 15 17 19 21 23"},"unifinder-todo-tree":{"widths":"0 0 0 0 0 0 0 0 0 0 0 0","ordinals":"1 1 1 1 1 1 1 1 1 1 1 1"},"unifiedToolbar":{"allowedExtSpaces":"{\"wa-in-th@ftassy.github.io\":[\"mail\",\"addressbook\",\"calendar\",\"tasks\",\"chat\",\"settings\",\"default\"],\"te-in-th@ftassy.github.io\":[\"mail\"],\"notebird@saveriomorelli.com\":[\"mail\"]}","state":"{\"mail\":[\"get-messages\",\"write-message\",\"address-book\",\"spacer\",\"ext-notebird@saveriomorelli.com\",\"ext-te-in-th@ftassy.github.io\",\"ext-wa-in-th@ftassy.github.io\"],\"addressbook\":[\"spacer\",\"spacer\"],\"calendar\":[\"synchronize\",\"new-event\",\"tasks\",\"edit-event\",\"delete-event\",\"spacer\",\"ext-wa-in-th@ftassy.github.io\"],\"tasks\":[\"synchronize\",\"new-event\",\"tasks\",\"edit-event\",\"delete-event\",\"spacer\",\"ext-wa-in-th@ftassy.github.io\"]}"},"folderPaneGetMessages":{"hidden":"true"},"folderPaneWriteMessage":{"hidden":"true"},"folderPaneHeaderBar":{"hidden":"true"},"quickFilterBarSticky":{"enabled":"false"},"threadPane":{"view":"table"},"threadPaneHeader":{"hidden":"false"},"columns":{"widths":"subjectCol:603.3333129882812"}},"about:preferences":{"paneDeck":{"lastSelected":"paneGeneral"}},"chrome://messenger/content/messengercompose/messengercompose.xhtml":{"msgcomposeWindow":{"sizemode":"normal","screenX":"691","screenY":"0","width":"874","height":"816"}},"chrome://messenger/content/messengercompose/EdLinkProps.xhtml":{"location":{"offsetX":"7"}},"chrome://mozapps/content/downloads/unknownContentType.xhtml":{"unknownContentTypeWindow":{"screenX":"690","screenY":"305"}},"about:accountsettings":{"account1":{"open":"false"},"account3":{"open":"false"},"account4":{"open":"true"},"account5":{"open":"false"},"account6":{"open":"false"},"account2":{"open":"false"},"account7":{"open":"false"}},"chrome://messenger/content/subscribe.xhtml":{"subscribeWindow":{"width":"494","height":"400","screenX":"9","screenY":"9"}},"chrome://messenger/content/FilterListDialog.xhtml":{"filterListDialog":{"screenX":"451","screenY":"174","width":"814","height":"539"}},"chrome://messenger/content/activity.xhtml":{"activityManager":{"screenX":"10","screenY":"10","width":"499","height":"339","sizemode":"normal"}}}
Se elimino xulsotre.json perdo buona parte delle informazioni della UI ma il menu resta sempre al suo posto. Se però avvio in modalità risoluzione dei problemi il menu torna dove dovrebbe stare secondo supernova.
Se elimino pref.js perdo gran parte dei settaggi tra cui anche la posizione della barra dei menu... quindi la voce è la dentro... rimane da capire quale.
PS: Qualunque trucchetto abbia usato ho appena scoperto che provoca il mancato funzionamento del tasto f10 per far scomparire la barra dei menu.