FYI - I needed two Injectible Content in same line in UX panel without linebreaks. I tried div and span tags with display: inline-block; or display: table-cell - did not work.

I ensured that these do not have any line breaks in the objects within or end of them.

The following worked.
<table border="0" cellspacing="0" cellpadding="0">
<tr>
<td>
{ContentFromInjectibleContainer: INJECTIBLE_1}
</td>
<td>
{ContentFromInjectibleContainer: INJECTIBLE_2}
</td>
</tr>
</table>

Regards.