Se añadió un campo a los appointments desde el home_page con la funcion citaId, esto permite desplegar la informacion de la cita en el screen Cita.js usando el mismo parametro en ambos queries, el de los threads y el del appointment

screens/main/Cita.js

    const [threads, setThreads] = useState([]);  
    const [loading, setLoading] = useState(true);
    console.log("ID", route.params);
+   const [appointments, setAppointments] = useState([]); 
 
 
 
       }
     });
 
+    const cita = firebase.firestore().collection('APPOINTMENTS').where("citaID", "==", route.params.tag._id).onSnapshot(snapShot => {
+      const appointments = snapShot.docs.map(docSnap => {
+        return{
+          _id:docSnap.id,
+          new:'',
+          Day:'',
+          Month:'',
+          Time:'',
+          i_token:'',
+          u_token:'',
+          Pin: {},
+          ...docSnap.data()
+        };
+      });
+      setAppointments(appointments);
+      console.log("appointment", appointments);
+    });
+
     return () => {
       fire();
+      cita();
     }
   }, []);
     
           </TouchableOpacity>
         )}
         />
+        <FlatList style={{
+           flex: 1,
+           width: screenWidth,
+       }}
+        data={appointments}
+        keyExtractor = {item => item._id}
+        ItemSeparatorComponent={() => <Divider />}
+        renderItem = {({item}) => (
+        <TouchableOpacity
+        onPress={async () => {
+          console.log("cita")
+        }}
+        >
+          <List.Item
+            title={item.Month}
+            titleNumberOfLines={1}
+            titleStyle={styles.listTitle}
+            descriptionStyle={styles.listDescription}
+            descriptionNumberOfLines={1}
+          />
+          <List.Item
+            title={item.Day}
+            titleNumberOfLines={1}
+            titleStyle={styles.listTitle}
+            descriptionStyle={styles.listDescription}
+            descriptionNumberOfLines={1}
+          />
+          <List.Item
+            title={item.Time}
+            titleNumberOfLines={1}
+            titleStyle={styles.listTitle}
+            descriptionStyle={styles.listDescription}
+            descriptionNumberOfLines={1}
+          />
+        </TouchableOpacity>
+      )}
+          />
       <Button
         title ='Ver mapa'
         onPress= {() => navigation.navigate('Map', {View_Only: true, Pin: Pin})}

screens/main/Home_page.js

     }
 
   }
+
+  function citaId(citaID) {
+    firebase.firestore()
+      .collection('APPOINTMENTS')
+      .doc(citaID)
+      .update({
+        citaID: citaID,
+      })
+  }
   
   check_user_type_INT();
   console.log("interpreter", interpreter);
               title ='Pedir Cita'
               onPress={ async () => {
                 await sendPushNotification(item.i_token);
+                citaId(item._id);
                 }
               }
             /> 
                 title ='Pedir Cita'
                 onPress={ async () => {
                   await sendPushNotification(item.i_token);
+                  citaId(item._id);
                   }
                 }
               />