How to deal with a cell having many lines of text that extend beyond the visible area? How to scroll through the content inside the cell?
Steps
- Set the row height small enough to fit fully on screen.
Right-click the row number on the left side of the sheet.
Choose Row Height…
Enter a height value that fits your screen comfortably (for example, 5-20 cm).
This ensures the entire row is visible without being cut off by the window.
- Enter cell edit mode.
Double-click the cell with the multiline text to start editing it directly in the cell.
- Use keyboard navigation to scroll inside the cell.
While editing, use the Up/Down arrow keys or Page Up/Page Down keys to move through the lines inside the cell.
This lets you scroll through all the lines without changing the row height or affecting other cells.
Notes
- This method only works when the cell is in edit mode (double-clicked).
- The row height must be small enough so the entire row fits in the visible window; otherwise, the cell content will still be clipped by the window.
- It’s a handy way to quickly scroll through large multiline text without using the formula bar.
since this topic seems to be a sort of FAQ,
- Text in cells is not wrapping by increasing cell vertical size
- Very long text in one Libre Calc cell. Hide/unhide tool?
here’s a " not recommend" option by @JohnSUN 
libreoffice calc - Display long string with left and right and dots middle - Stack Overflow
Sorry about the mistake, it does require changing row height. I told the technique to an AI for it to redact the message better.