From scratch TYPO3 don’t allow to edit files with file extension “ts” to be edited in the fileadmin of the backend. Allthough it is a good way to hold configuration directives in files with this suffix.
Start the install tool
Go to “all configuration”.
Find the key “[SYS][textfile_ext]”.
Add “ts” in the field, but with a comma.
Save with “Write to localconf.php”.
Reload the fileadmin page.
If necessary flush the cache.
The you can see the edit icon in fileadmin list.