How to change an indent for hanging indents in Pages

If you haven't done so already, start with showing the rulers - View > Show Rulers or ⌘R. Then click & hold on the bottom part of the indent marker, the inverted triangle, & drag it to the location you want the indent to be. Then click & hold the tiny top bar of the marker to the left to create the hanging indent.

It's next-to-impossible to see the two separate parts unless you zoom in. It can be trial & error to grab it. You can use System Preferences > Accessibility > Zoom to set a shortcut to easily zoom in.

Select the paragraph you want to indent.

On the Text tab of the Format inspector, click the disclosure triangle beside the word "Indents". You will see controls that say "first", "left", and "right". When the "first" number is greater than the "left" number, you get a first line indent. When the "left" number is greater than the "first" number, you get a hanging indent. When the two numbers are equal but not zero, you get a paragraph left indent. The "right" number gives you a paragraph right indent.

In my Pages '09 version 4.3, I can do the following. I don't know if you can do this with your version of Pages.

To move the left indent marker independently of the first line indent marker, first hold down the Option key and then press down on the trackpad and option-drag the left indent marker with the arrow cursor.

To move the first line indent marker independently, position the arrow cursor over it and then drag the marker.

Hold down the Command key while dragging the three indent markers to position them precisely, otherwise the markers will be positioned at the nearest tick mark on the ruler. Release the trackpad before you release the Command key. This keyboard command also works for tabs (Arrow cursor) and the document left and right margins (SplitH cursor).

To move the left indent marker independently and precisely, first hold down the Option key and then press down on the trackpad and option-command-drag the left indent marker with the arrow cursor. Release the trackpad before you release the Command key.