Trace elements

Old French had fragments of Latin decelensions in masculine nouns:

li murs (the wall, subject) || li mur (the walls, subject)
lo mur (the wall, direct object) || les murs (the walls, direct object)

Old Provençal followed the same paradigm:

li jorns (the day), li jorn, lo jorn, los jorns

The modern Surselvan dialect of Romansh preserves this nominative -s for adjective complements of masculine nouns:

Il Bab en tschiel ei buns (The Father in heaven is good).

BUT -- Il bun bap (the good father).

Romanian has combined nominative/accusative and genitive/dative forms of the noun:

o casă (a house, feminine) nom/acc
nişte case (some houses) nom/acc
unei casă (of a house, to a house) gen/dat
unor casei (of some houses, to some houses) gen/dat

There is also Romanian vocative:

Ion (John) -- Ioane! (O, John!)
Maria (Mary) -- Mario! (O, Mary!)

Does anyone of other post-Latin examples?

In Portuguese when you are calling to someone it is usual to use O before the proper name.
My Portuguese husband when he speaks to one of our daughters called Ana (they revised the spelling of this years back from Anna) always used something that sounded very much like Ohwanna. Even my Portuguese native speaking children have a giggle at this.

Speaking of giggles, way back when, Spanish briefly borrowed the Arabic vocative particle "ya" to do the same thing, merrily using it right alongside the Spanish adverb "ya," meaning "already" or "now."

As in "Ya habibi?" ("Hey, my friend") --

Yes, except "habibi" is more like "sweetheart"! Friend could be "sawdiqi" instead.

I don't think the Ablative case in Latin has any traces in any modern Romance language. However, English has something of an ablative trace in two words which are really adverbial: thence which means from there, and whence which means from where.