I would do a two step approach – in 1st step you could select appropriate log and in 2nd you will create a new comment to it.
With one step (page) with your current model it could looks like this:
Michal
P.S: Try to use best practices for naming (https://docs.mendix.com/howto/general/dev-best-practices#3-naming-conventions) like camel case, using singular, not using underscore..., otherwise everyone will get lost in your code.