When using the Block editor (rather than, say the WYSIWYG editor), click / select the line you made — sounds like three asterisks — then as soon as you do that, on the right side, the Block Editor displays another button ellipsis: click that, then you can choose from the line style you want: a ‘simple’ horizontal line (= wide line), or shown as 3 asterisks (= Dots), or shown as a single asterisk (= Dot). Finally, click anywhere on the page. You should then see your preferred line style displayed.
