Language - ManicTime is offered in a few languages. If you would like to translate it to some other language not on the list, you can read more about it here
Theme - Change the look of ManicTime
Show current time indicator - A red line indicating current time will be shown on the timelines
Show tag notes in day summary - Notes will be displayed in bottom right part of Day view
Show overnight Away - If you leave your computer running through the night, it will show up as Away time. Let's say you are interested in knowing how much Away time you have only during the work time. If you uncheck this, overnight Away time will be hidden, so only Away time during the work day will be shown.
Use decimal hour format for day summary and Use decimal hour format for statistics - decimal hour format is displayed as 5,5h while normal hour format would be 5:30.
Add notes to 10 recent tags - when checked notes will be part of the context menu which shows 10 recent tags