Is there any way we can monitor the progress of spiritual enlightenment? How does a person know what stage he is at?

Respected Aadhik Ji, it is a process of transformation and an inner quest. When one starts feeling unaffected by what is happening in the external world and is peaceful inside is a good sign. Also, such an individual has recognized the divine light inside and is connected with the source.
ਤੇਰਾ ਕੀਆ ਮੀਠਾ ਲਾਗੈ ॥
ਹਰਿ ਨਾਮੁ ਪਦਾਰਥੁ ਨਾਨਕੁ ਮਾਂਗੈ
Such an individual knows his/her capabilities in terms of creativity, strength and is on the path of success.
ਸਭੁ ਤਨੁ ਮਨੁ ਹਰਿਆ ਹੋਇਆ ਨਾਨਕ ਹਰਿ ਵਸਿਆ ਮਨਿ ਸੋਇ