A lot of things can be changed in ManicTimeServerSettings.json configuration file. Most common thing which you will change is connection strings to the database if you use MS SQL or PostgreSQL database engines. But there are many more settings. You can see all possible settings in ManicTimeServer folder.
By default, you will find ManicTimeServerSettings.json file in server's data folder Windows
c:\ProgramData\ManicTime\Server\ManicTimeServerSettings.json
Linux
[ManicTimeServer folder]/[Data]/ManicTimeServerSettings.json
On Docker, if you follow our example, your data folder will be in:
/var/lib/manictimeserver/Data
It is possible that the file is not in the folder if you use all the defaults. So for example if you use SQLite database, if you use port 8080, which are all default values. If this happens, just create file ManicTimeServerSettings.json and put it in server's data folder.
You must always restart the server, after you make changes to the file.