Secure the ELK password in config files

Elastic Stack Elasticsearch
1

I'm using x-pack to secure ELK stack , I don't want to specify plain text "password" in ELK Config files. Is any way to encrypt & decrypt

2

You should go through this:
https://www.elastic.co/guide/en/x-pack/current/setting-up-authentication.html#set-built-in-user-passwords
and this:
https://www.elastic.co/guide/en/elasticsearch/reference/6.2/secure-settings.html