Tab decreasing font size

In this doc, on pressing Tab at the beginning of a line, except the 1st line, the font size decreases. Which function is this?

Thank you for helping.

Build ID: dcf040e67528d9187c66b2379df5ea4407429775
CPU threads: 4; OS: Linux 5.4; UI render: default; VCL: gtk3
Locale: en-IN (en_IN); UI: en-US
Calc: threaded

Don’t use tabs or multiple spaces to indent text when you can get the indentation by other means. As you can always get indentation by other means, that means that you shouldn’t use them at all, except in very simple documents.

Press F11 to open the styles overview. Right click in Heading 1 and select Modify. Use the Indents & Spacing tab to indent your text (Before text).

You are probably a beginning user of styles in LibreOffice. Take some time to get comfortable with them. Take a good look at each tab on the dialog box, you will find that you can modify formatting in many ways that you hadn’t thought of were possible. It will make life a lot easier for you. Don’t wait with exploring LibreOffice until the moment that you are in a hurry to meet a deadline.

Your text is formatted with Heading styles. Pressing Tab denotes a heading by one level, hence the change in the font size. Learn to use paragraph styles.

Thank you, but why the same is not happening with the first line which also is a heading style?

Your collection of Heading n paragraphs makes a list. Lists have additional properties compared to ordinary paragraphs. One of these is the ability to promote/demote items to another level with Tab or Shift+Tab at the very beginning of the item. But if Tab is used on the first item, the whole list is shifted to the right, probably because promoting/demoting the first item does not make sense.

However, I am not convinced this is not a bug because I can’t find any mention of it in the documentation.

great explanation, thanks a lot, I admire your ablity to explain things.

I knew this for a list but didn’t expect that a continuous group of headings would act as a list.

The heading mechanism is based on the list engine. But headings are a very special list: the sequence counter depends on Tools>Chapter Numbering instead of a common list style and levels are formatted with a dedicated paragraph style instead of a single one for ordinary lists.