[calimero66]

Here is an example with an annoying line-break after "Ein Haufen":

At first the original (german) e-book:

Ein Haufen

aus Knochen und verwesendem Fleisch

This is the view with SIGIL:

Ein Haufen&nbsp;</p>

<p class="calibre5"></p>

<p class="calibre4">aus Knochen und verwesendem Fleisch

Now I want to delete the '&nbsp' with the following </p>.
In Calibre it is not a problem to find the text position:

But if I use \s</p> as Search Regular Expression, it will be ignored (irrespective of the Replacement Text)

By the way, it is no problem to replace </p> or <p class ... without the &nbsp;