From examples such as https://www.emarketstorage.com/storage/20200530/20200530_804... it seems likely that your expression comes from a balance sheet published “ai sensi dell’art. 114 d.lgs 58/1998”, in which case the expression would essentially be an abbreviation of the balance sheet subtotal “Totale posizione finanziaria a medio lungo termine”, and that the other subtotal would be “Totale [posizione finanziaria] a breve termine”.

First of all, given that “Totale a breve termine” and “Totale medio lungo termine” add up to the company's complete total, "medio lungo termine" cannot be translated as “medium- TO long-term” but must instead be translated as “medium- AND long-term”.

In Italian, the intermediate wording “posizione finanziaria” can be omitted in the title of this subtotal, but in English it cannot be dealt with in quite the same way. How it should be dealt with in English depends on whether you want UK English or US English. Because I am not an expert in UK English, I will discuss only US English usage.

Searching on Linguee, I see that Italian companies themselves consistently translate “posizione finanziaria” directly, as “financial position”. However, this expression is rarely used in US balance sheets. (In US annual reports or 10-K forms, it is used in the discussion and in the auditor’s report but not in the balance sheets themselves.)

In equivalent US balance sheets (such as can be found by searching the SEC’s EDGAR database, at https://www.sec.gov/Archives/edgar/data/), it is not the case (as far as I can see) that assets and liabilities are ever grouped together under either “short-term” or “medium- and long-term”. Instead all assets are listed in one table, and all liabilities are listed separately in another table (along with shareholders’ equity). So, you are probably dealing with an Italian type of balance sheet that has no equivalent among standard US corporate balance sheets (though something similar might be presented in the notes to the financial statements).

In addition, in the US the terminology does not divide assets or liabilities into “short-term” and “medium- and long-term” but instead into “current” and either a list of individual other items (in the case of assets) or “noncurrent” (in the case of liabilities). This means that the data in your table may be insufficient to convert the table into a standard US balance sheet.

In any case, if you are writing for a US audience, I would suggest that instead of “medium- and long-term” you use the term “noncurrent”. And I would not omit the equivalent of “posizione finanziaria” but instead (as in US balance sheets) write it out in full. I would therefore suggest the following:

“Total noncurrent assets and liabilities”

This form has the advantage of using US accounting terminology (i.e., “noncurrent”, “assets and liabilities”) while at the same time not altering the categorization used in the Italian original.