been there tried that - see older threads.
problem is you don't usually just have <p> text, you have <p class="calibreX" > text and you can't apparently have <p class="whatever" as well as "text-indent: 0" all in the same line.
so you have do define a new class - calibreY with the no indent property..... which means opening & editing the .css file....
it's all doable, just more work than slotting in a quick <br> tag