you can use sed for dynamically adding some values

for example:-

apiVersion: apps/v1
kind: Deployment
metadata:
  name: logstash-deployment
spec:
  selector:
matchLabels:
  app: logstash
  replicas: 2
  template:
    metadata:
      labels:
        app: logstash
    spec:
       containers:
       - name: logstash
         image: logstash:6.8.6
         volumeMounts:
         - mountPath: /usr/share/logstash/config/
           name: config
          - mountPath: /usr/share/logstash/logs/
            name: logs
       volumes:
       - name: config
         hostPath:
           path: {path}
       - name: logs
         hostPath:
           path: "/var/logs/logstash"

Now I want to add dynamically add the path

I will simply

set -i "s|{path}:'/etc/logstash/'|g" deployment.yml 

In this way, you can put as many values as you want before deploying the file.

There are some fields in kubernetes which you can get dynamically like node name, pod name, pod ip, etc. Refer this (https://kubernetes.io/docs/tasks/inject-data-application/environment-variable-expose-pod-information/) doc for examples.

Here is an example where you can set node-name as an environment variable.

env:
        - name: MY_NODE_NAME
          valueFrom:
            fieldRef:
              fieldPath: spec.nodeName

You can change your deployment in such a way that it creates a file by adding node name to it.. In this way you can have different file name on each node. Recommended is to create a daemonset instead of deployment which will spawn one pod on each selected nodes (selection can be done using node selector).