Selected text size changes with the font size

How to enable this option of “selected text size adjusts with the font size while scrolling up and down over the list of numbers after clicking font size button” in Writer and Impress?
The selected text size should change when I scroll up and down over the list of different font sizes.
Selected text size should decrease with the font size as I move up the mouse pointer over the list of numbers.
Selected text size should increase with the font size as I move down the mouse pointer over the list of numbers.
Example: Selected text size should instantly change and show its size as 14 after I move the mouse pointer over font size 14.
Similarly selected text size should instantly change again and show its size as 24 after moving the mouse pointer over the font size 24.

This would record a bunch of changes making Cancel a nightmare.

Anyway, for any “serious” work, you shouldn’t use toolbar buttons or menu but styles.

Hello,

How to enable this option of “selected text size automatically adjusts to font size while scrolling up and down the font size button” in writer?

You can’t - there is no such option.

This is not the preview tool you are looking for. Maybe you want to choose a font size before creating styles to suit a particular layout but you don’t know how it will look. This is a reasonable thing to do when trying out layouts.

Select your text

  • By mouse, open the sidebar, click on
    the Properties icon. Just below the
    font size box there are two icons, a
    large A with an upwards arrow and a
    small A with downwards arrow, click
    one or the other and each click will
    change the selected text by one font
    size (might be 2 points or bigger
    difference between previous and
    current).
  • By Keyboard. Press Ctrl+] to increase
    font size or Ctrl+ [ to decrease font
    size.

You wouldn’t want to use this tool in a document that you have started because it will override your styles making changes to styles a nightmare and will fill your undo list with trivial changes. However, while you are deciding on fonts and appearance it is a quick and dirty tool.

I want to increase my font to 450

You’re welcome.

@LoriGreen If you want to set your font size to a specific size, you can select your text and just type the new size in the Font Size box, or in Format > Character in the dialog box, in tab Font, under Size type 450 and OK.

450 point works in LibreOffice but on A4 you can do only one or two letters before it goes on to the next page. My guess is that you have already set a custom page size.