You could do a Loop condition action with a condition that says while 1=1. This will create an infinite loop. Then use a If web page contains and check if the 'Load more' button exists. If it does, then use Press button in web page to press it. Else, use Exit loop to stop your loop.
This is the standard practice. You could also do the same with a JavaScript function.
If you don't want it to go all the way until there are no more reviews to load, you can also use the If web page contains action to check for text rather than an element on the web page. So, you can check if the web page contains the text 'a month ago'. If it does, then use Exit loop to stop pressing the 'Load more' button.
