Generally, It is not recommended to write events on LUs related to common framework used in different LUs/Screens, as this could impact the server performance, since data will follow from multiple processes.

I don't think the pre posting table can be considered a framework table. It might still be a bad idea though, especially if there is a high volume of transactions in that table, but I don't know much about that. Why not try and see? It's easy enough to disable the custom event if it affects performance.

We have created custom event and found no issues as it is working fine as per the requirement. one of IFS partner mentioned that it is not recommended to create custom event on Pre-Posting table so I wonder does IFS R&D has any such recommendations or guidelines.

I am assuming you are trying to restrict users from using code part combinations that are not valid? Ex: Dept A, Location X is not a valid preposting. If that is the case, why not use combination rules?

I don’t think we have but if we had it would probably be part of our technical documentation which is available publicly at docs.ifs.com.