@R.T.: “Shabbos Mincha; no special nigunnim in Tefila (unlike Lecha Dodi, Kel Adon)
Shalosh Seudos — simple food, bread, salads, etc…
We see from the above that the theme is more of simplicity, straightforwardness.”
interesting you say this, even though it’s a norm to serve left overs, and in some populations even leave out seuda shelishis, Rav Pinkus ZT”L in his book ” NEFESH CHAYA” states how important shabbos is and it is very wrong that people think less of seuda shelishis than friday night meals.
Seuda shelishis should not be a less of an important meal. he gave a classic example of shabbos b4 pesach he had a custom in his house to use proper china and not plastic goods in order to honor the shabbos properly.(even though these days plastic goods look amazing, on his level it was somehow disrespectful for shabbos)
So even though it’s a norm to be more relaxed and simple towards the end of shabbos don’t take it as the right thing to do / behave.