In order to make targeted improvements to the performance of the application, I investigate which actions take the most time.
I've found that there is a field 'duration_ms' in the table 'use_log_usr_action' in the IAM database for that. However, the field contains no data.
Is this field created for future features or should an specific option/property be set for it?
Well Harm, the field had been there since version 2017.2 and I can only find two records in that table on our internal IAM database which have this field filled. I guess this was part of an experiment and sneaked into production which normally never happens. And now you have found it 
I'll discuss this internally what to do with this field. Nevertheless, it's certainly a good idea to be able to see what actions take the most time.
Edited on 2022-01-20: Fields are not being used currently but will stay part of the table in case the feature of User preferences in Universal GUI needs these
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