Final Cuto Pro X sort by modified date
Seems like the question is asked on other places as well, with no answer so I will propose a workaround as I don't think FCP X gives you option to sort by Modified metadata field.
Bash script that adds a modification date at the beginning if each file in the directory in epoch. Then sorting in FCP by name.

Open terminal and go the the directory you want to apply changes (in my case a directory with videos).
do cat &gt; script.sh
Enter: for f in *; do mv -- &quot;$f&quot; &quot;$(stat -f %m &quot;$f&quot;)-$f&quot;; done
Hit enter and then ctrl + D
Now type: bash script.sh
Open FCP X and do Sort by: name

Note:
In order to revert the process, all you have to do is to replace what is in the point 3 to: for f in *; do mv -v &quot;$f&quot; &quot;${f#*-}&quot;; done