I’m not sure how you mean “in the THEN area of the UI”. Did you remove the Script Actions? Do you really mean that you added a but only if… condition to block the rule? Or did you click the || pause icon at the top of the Rule?
A lot of the more simple rules don’t even need code. See [wiki] Getting Started with OH3: rewriting the tutorial - 8. Rules (will become a part of the Getting Started Tutorial soon I hope.
There are a number of JavaScript examples for doing some things in Experimental Next-Gen Rules Engine Documentation 4 of : Writing Scripts (follow the links at the bottom to the Actions page too which will show how to create a Timer). Keep in mind I wrote that years ago now and there might be some things that are not quite current at this time. For example, Anytime you see DateTime you need a ZonedDateTime instead.
There are some more JavaScript examples of some more advanced rules at OH 3 Examples: Writing and using JavaScript Libraries in MainUI created Rules.
There are tons of Python examples on the forum including in all of the Design Pattern posts. However, those are all written from the perspective of writing rules in .py files and not through the UI and using the Helper Libraries. But they still work as piece part examples for how to do things like creating Timers and such. At some point soon hopefully the helper libraries will be available as an add-on so those examples will become more relevant.