Option to add custom metadata

What TMM version are you using?

Version 5.1.5 release

What is the actual behavior?

Fixed tags/metadata for all movies and shows based on the data from IMDB, TMDB etc.

What is the expected behavior?

I would like add custom metadata like it is already possible with the tags or genre section. My current use case is to dim up the lights when the movie credits start. As the credits never start at the same time, I am looking for the time in seconds, when the movie credits start and put them in a json for my home automation to see how many seconds already played and the at the credits execute an automation to dim up the lights.

So it would be great to have an option to device custom metadata like "credit start time" and then enter a value. Currently, there are fixed metadata like "source" where you can select "TV", "Bluray" etc. Also the runtime of the movie or the edition can be set. But a custom section would be great.