In Mac Excel, how can I replace with newline?
Manually Adding a Line Break
You can do this by pressing Option Enter at the point you want to insert the line break.
It's best that you format the cell(s) as Text to ensure the best results.

Mass Insert Line Break (a.k.a Search/Replace)
You can do this on a mass basis with Search &amp; Replace.  As before, it's important to format your cells as text.  In the replace field, use the generic formula
=&quot;Text1&quot;&amp;CHAR(10)&amp;&quot;Text2&quot;&amp;CHAR(10)&quot;Text3...&quot;


The text to be replaced in quotes (&quot; &quot;)
&amp; as the concat (concatenate) function
CHAR(10) as the symbol for newline

Using this methodology, you can &quot;fix&quot; multiple lines of text (like an address).  See the animation below for an example: