WordPress Staging Site

I fear that there does not exist an answer that is going to make you happy. There is no (easy/good) solution for this problem. In most cases, the production (staging) environment does only touch the code (FTP-files) of a WordPress website, while the live version makes changes to the database (e.g. adding content to it). So normally, when you want to update the live version, you (Git) pull the new version of the website onto the server, and do not touch the database. Additionally, one could change some minor settings within WordPress manually, which will update the database.

However, in the particular case you describe, using Page Builder to develop new features/pages on the staging website, both the staging version and the live variant of the website are making changes to the database.

As far as I know, the only method to update the live website is to find out which database records are updated by Page Builder and add these to the live database manually. The only ‘real’ solution that I would know of is to create new features in the code itself, but I can see how this might not be a solution for you.

TL;DR: both variants (stage/live) make changes to the database, they have to be merged which is not trivial.