Related: T130496: API sandbox's descriptions are positioned and styled poorly

There's probably not any need for the indenting provided by the <dd>s here at all. But do maintain the separation of items by wrapping each thing that's currently a <dd> in some other block element.

some other block element like a <div> for example ?

Yes, <div> is a block element that could be used.

The <span> is the key issue here. It should be a div to allow for semantically correct new elements insertion. Changing from <dl> to other elems, is not a solution.

I tried to change the <span> that contains the <dl><dd>description</dd></dl> into a <div> and the API sandbox remains the same. Is there a page where the abuse takes place so I can try and fix it ?

This is done in resources/src/mediawiki.special/mediawiki.special.apisandbox.js, search for <dd>.

Change 339945 had a related patch set uploaded (by Kosson):
Don't use <dd> for indenting descriptions on Special:ApiSandbox

https://gerrit.wikimedia.org/r/339945

So, I fixed @Kosson's commit to use block-level elements (e.g. imbricated divs). It might be just me, but I think the indentation looked nicer. Would it be enough to add a new class with margin-left: 1.6em for the outer element?

Comparing the two side by side, I like the version without the extra <dd> whitespace better. The description and info is still indented relative to the field name, just not by quite as much.

Change 339945 merged by jenkins-bot:
Don't use <dd> for indenting descriptions on Special:ApiSandbox

https://gerrit.wikimedia.org/r/339945