The final 10-letter word is:
Find this by noticing that the two lists of capitals provided are...
...the capitals of countries with horizontal tricolour flags (headed by '-'), and the capitals of countries with vertical tricolour flags (headed by '|').
In both cases these are ordered alphabetically by the names of the countries. Thus we need to find the capital cities for the countries that would fit alphabetically into these slots, having the appropriate tricolour flag orientation.
This means our missing capitals are:
Bogo[t]a (of Colombia)
Cai[r]o (of Egypt)
Tripol[i] (of Libya)
Asun[c]ion (of Paraguay)
Pret[o]ria (of South Africa, when using the 1928-1994 flag that appears in the list of tricolours on this Wikipedia page, which I suspect the OP was referring to when creating this puzzle...)
Brusse[l]s (of Belgium)
[O]ttawa (of Canada)
D[u]blin (of Ireland)
Yamoussouk[r]o (of Ivory Coast)
Buchare[s]t (of Romania)
To get the final 10-letter answer, we must...
...use the numbers in brackets to help us extract the letters in that numbered position within the names of the capital cities (e.g. the 5th letter of Bogota is 't') and read them down the list. I have indicated these in the lists in the previous spoiler using square brackets. This gives us the appropriate answer, TRICOLOURS.
(And regarding the title, I expect the 5-letter word missing there is 'FLAGS'...)