Preliminary remark: your list is defined by a custom list style (Elenco numerato link [n]) which effectively attach all your items to the same abstract list. This is good.
“Structural” remark: IMHO text made of Elenco Bibliografia [] (not sure about the last character(s)) and Riferrimenti ai testi paragraphs belong “logically” in the list at different levels (1 and 2). To communicate this logical relationship to Writer, you should integrate the Riferimenti … paragraphs in the list.
Now to the core of the problem.
Obviously your document has a long and erratic editing history. This is aggravated by your character-level direct formatting (though theoretically there should be no interference but the XML shows a really cluttered encoding. Character styles are your friends (like all other styles) and you would surely benefit from using them instead of your present direct formatting (colour, bold, italic, superscript, …).
This direct formatting plus the editing history contribute to a huge size inflation of your document. This 1-page sample should not weigh 88kB. Direct formatting (creating single-use anonymous styles) is responsible for the majority of this size.
During your edits, you probably caused numbering reset in your list. I tried to fix this but I could not, probably because the erratic attempts have “corrupted” the encoding, preventing the fix for the attribute.
I removed the list style application, reverting your text to ordinary paragraphs. Since the list style is applied only to Eleco Bibliografia [] (at least in this sample) and this paragraph style has no other usage than this list (again in this sample), I reconfigured the Outline & List tab of the paragraph style to associate it systematically to the list style. Consequence: you no longer need to apply manually the list style; it comes automatically with the paragraph style.
This solved the numbering reset.
Then, following my suggestion about the “child” Riferimenti … paragraphs, I modified the list style to configure its level 2 to Bullet with U+2514 BOX DRAWINGS LIGHT UP and RIGHT└ as the bullet. Position of level-2 was adjusted to align it at left below level-1 text.
Aesthetic tuning: Times New Roman is not installed on my Linux box. I had to use Liberation Serif for the “bullet”. This font has not the same metrics as TNR (or the face it was substituted). If I align the bullet at 1cm (the level-1 indent), the “bullet” is slightly indented to the right. I had to set 0.95cm to have it correctly visually positioned. This may not be necessary on your computer. Check.
I removed the manually inserted strings to avoid duplication. Since I could not determine if Riferimenti ai testi had other usages (and it is also the ancestor of other styles), I applied manually the list style and pressed Tab to promote the items to level 2.
Here, a new problem occurred. Level-1 items were then numbered 1, 3, 5, 7, … This is caused by an incorrect configuration in list style Elenco … where Consecutive numbering is ticked. This setting requests that all items, no matter their level, are numbered sequentially as if they were all at level 1. This is usually not what users want.
One last remark. Apparently, empty paragraphs Spazion 5 tra periodi are used to vertically space your text. This is very bad practice because it inserts meaningless (read: contain no useful data) “objects” in your document and sooner or later they will ruin you layout (after editing, your text is reflown and some paragraphs may be flushed to next page, thus detaching the spacing “objects” from their child paragraphs).
To compensate, I modified Elenco … Indents & Spacing tab to incorporate the spacing in Above paragraph setting.
See the modified document: prova_libre-ajl.odt (28.1 KB). Note that the partial direct formatting elimination reduced the size to 28kB.
