Did you consider using a menu sort order so that the plugin part will automatically be left out without the plugin?

No, I didn't. You're thinking about making these available also for android devices where coverbrowser is disabled?
Not sure how to do that, how would you do that ? (while keeping the other items self contained in the plugin, without leaking their ids into core ?)

edit: Not involving menu sorter, it could be easier to, even for android, registerToMainMenu() in CoverBrowser:init(), and in CoverBrowser:addToMainMenu(), build a different menu if android / others.
But the same "Display mode > Other Settings > these 3 new settings" would be a little awkward. How would you name it for android: "Display settings > these 3 only settings" ?

You'd add another entry in the menu_order definition:

    filemanager_display_mode = {
        "plugin_stuff",
        "more_plugin_stuff",
        "----------------------------",
        -- the above will simply be ignored by MenuSorter if plugin_stuff is nil
        "core_stuff",
        "more_core_stuff",
    },

I spent most of my time on MenuSorter making sure it could deal with such situations without breaking (except I never thought to throw the separator thing at it). Most submenus are done the traditional way but in principle many of them could be migrated to the MenuSorter system, even if only internally.

That is, you could define your own menu using the MenuSorter method while still keeping it out of the main loop.

plugin_menu_order = {} -- you know how this works
plugin_menu.whatever = {text="etc"}
menu_items.my_plugin_name = MenuSorter:sort(plugin_menu, plugin_menu_order)

In fact that might be preferable to keep plugin configuration separate. On the flip side, in that case you can't reorganize the entire menu at your personal whim.

Anyway, those are just some possibilities I explicitly designed in there but which aren't currently used much if at all. :-)

edit: Not involving menu sorter, it could be easier to, even for android, registerToMainMenu() in CoverBrowser:init(), and in CoverBrowser:addToMainMenu(), build a different menu if android / others.
But the same "Display mode > Other Settings > these 3 new settings" would be a little awkward. How would you name it for android: "Display settings > these 3 only settings" ?

Something like "filemanager (display) settings"?

OK, made that menu with new 3 settings at 1st level named File browser settings on Android.
(I did not make menu sorter involved, as I somehow prefer the whole indented table definition for a better feel of menu hierarchy.)

It still itches me a bit that this core settings menu is defined here in a plugin. They could probably be in filemanagermenu.lua, (as self.menu_items.filemanager_settings), with both "filemanager_display_mode" and "filemanager_settings" in elements/filemanager_menu_order.lua, and this plugin could steal them from menu_item in addToMainMenu(menu_items) and unset menu_items.filemanager_settings = nil so main menu sorter ignores it.
Should I try that ? or would the current stuff do for now ?

No rewording suggestions ?

As you wish. :-P

Tried to put them into filemanagermenu.lua, but plugins/registered_widgets are added eartly to menu, before menu's own stuff, so in this plugin's addToMainMenu(menu_items) , the menu_items it gets does not yet has the keys set in filemanagermenu.lua... so I can not grab them to move them into Display mode. And it would pain me a bit to have 2 submenus on others than Android.
It would need some work on filemanagermenu.lua (may be just moving the registered_widget additions from early to late), but i'm not confident with changing things there that work :)
So, safer to let them in this plugin.

Updated wordings (including those from original coverbrowser not noticed weeks ago :).
(btw: is plural in "no images" ok in english ? I'm used to writing "aucune image" in singular in french).

(The "file changed" diff is a bit ugly, because I gain one indentation level by using if self.ui.view then return end)

(btw: is plural in "no images" ok in english ? I'm used to writing "aucune image" in singular in french).

That would depend on context. When in doubt you can always check on one of those sites like Linguee or Bab.la. They've usually got fairly decently translated stuff.

http://www.linguee.fr/francais-anglais/search?source=auto&query=aucune+image

For example, you've got this pair:

• Sans aucune image sur les écrans, c'est difficile de voir à quel point la console peut être attractive.
  nintendo.fr
• Without any images on the screens, it's difficult to communicate the full appeal of the console.
  nintendo.ru

(… nintendo.ru? Odd to get English from there, but whatever)

I think that in English zero probably always takes a plural form, unless it's a mass noun like sand or water. Of course you could always say that you don't have even a single image when you have pas d'images. :-P

Speaking of which, what's the difference between J'ai aucune image and Je n'ai pas d'images? To me the first sounds more forceful.

OK, so "no images" can stay.

Speaking of which, what's the difference between J'ai aucune image and Je n'ai pas d'images? To me the first sounds more forceful.

No real difference, and you're right about the forceful (and we use the negative in je n'ai aucune image)
I would always use singular with aucune image. Just read that with sans (without), it's singular or plural depending on how it would be avec (with) :) Un homme avec parapluie, un homme sans parapluie. But une chemise avec manches, une chemise sans manches.

we use the negative in je n'ai aucune image

It seems to me that even the n' is often dropped outside of writing.. ;-) But yes, that was a silly oversight on my part. Double negatives don't come naturally. I've managed to internalize a few of the most common ones like ne…pas, ne…plus and ne…jamais so they come out without thinking but that's about it.

It seems to me that even the n' is often dropped outside of writing..

Yes indeed, in talking, we easily drop the n', even the ne : j'ai pas de parapluie, je viendrais pas.