Changing Default Text
If you want to override any of Contao's default text, for example the "Read More" text for newslists, you will need to add a "langconfig.php" file in the "system/config" folder. Inside that file you just need to list the Global Variables alongside what text you want in its' place.
<?php // Using the newslist "Read More..." line as an example $GLOBALS['TL_LANG']['MSC']['more'] = "";
Finding Which $GLOBALS
If you need to find which $GLOBALS variable the text is assigned to you can search "In This Repository" on Contao's Github page. For example, I searched "Read More" on Github which turned up results showing $GLOBALS['TL_LANG']['MSC']['more']. By choosing the "In This Repository" option when searching it will check all of Contao, not just a specific branch.