As the Generate missing Glyphs couldn’t create the ì and í,
I’ve tried to edit the “i” as a vertical bar + the dotaccent component. But it didn’t fixed the issue.
So I’ve created the ì and í manually duplicating the “i” and changing the gliph name into iacute and igrave. But once I’ve made it, the 2 glyphs disappear while taking a placeholder in the general font view.
Ok sorry; I’ve undestood now 
I had to use “dotlessi”
By the way the “edit” button used to save the edited message still don’t work. I see a javascript error on line 107 in /templates/form.js “console not defined”
The disappearing is only a display bug. If you click anywhere in the sidebar and than back where you were, it should be there.
And I fixed the javascript error.
Don’t know… to get them visible again I had to change the names in a fake text (as aaaa). Then I could delete them and restart with the correct procedure.
Edited : I confirm, edit now works