A word of caution about cooking chilli beans / red kidney beans. If you are cooking these from dried beans, you need to give them a good 10-15 mins boil on a high heat to kill off the toxins. Without this, the beans can cause stomach upsets and even uncontrollable bottom accidents.
If cooking tinned ones there should be no problem, and once the dried beans have been fast-boiled and cooked through again no problem with re-heating.
It makes no difference if you reheat in a microwave or reheat in a slow cooker. In fact is is better once it has been cooked and cooled down and used the next day