I did it once, but cannot find out how any more:
how to keep the top row of my LibreOffice Calc sheet visible when scrolling?
(Intuitively it should be either in view or format, at best in right-click menu, but I can't see anything related ... )
You can achieve this by either splitting or freezing the spreadsheet. These two options are slightly different, the main difference being that splitting adds a second scrollbar, viewing the same sheet from two contiguous windows as it were.
How to split the spreadsheet
Using the mouse pointer:
How to freeze the spreadsheet
Thank you for your interest in this question.
Because it has attracted low-quality answers, posting an answer now requires 10 reputation on this site.
Would you like to answer one of these unanswered questions instead?