Mark name to Text Layer

txt = value;
n = 0; 
if (thisComp.marker.numKeys > 0){ 
n = thisComp.marker.nearestKey(time).index;
if (thisComp.marker.key(n).time > time) n--;
if (n > 0) txt = thisComp.marker.key(n).comment;
}
txt

(example with layer named CASTER01 with markers, the expression should fit inside a type object’s text field)

txt = value; n = 0;
if (thisComp.layer("CASTER01").marker.numKeys > 0){
n = thisComp.layer("CASTER01").marker.nearestKey(time).index;
if (thisComp.layer("CASTER01").marker.key(n).time >
time) n--;
if (n > 0) txt = thisComp.layer("CASTER01").marker.key(n).comment; }
txt