The old Firefox IDE supports a gigantic lists of commands, many of them rarely used or not at all. Simply adding this zoo of commands to a new IDE does not help the web testing community. In the new IDE we only want to support commands that are truly useful and used. Kantu's built-in flow control and webdriver-like implicit waiting make many old commands redundant. But if we missed an important old Selenium IDE command, please contact us and tell us which one and why.
The new Kantu IDE does not support extensions yet (If you need this feature, please contact us.). Note that for many functions the storeEval command provides a good, easy-to-use alternative. For example, creating random numbers is easily done with storeEval | Math.floor(Math.random()*11) | YourRandomNumber.
Selenium IDE commands, Classic Firefox Selenium IDE.