Thank you for your question.

You can change the length of a custom field using the Validation Expression in the Customizer.

Example to limit text to 4 characters : \d{4}

However, the same option is not available for the system fields such as the Summary field in the incident form. Hence this will be enhancement to the current system.

Please use the 'Create Ideas' button under the Ideas section or via the following link https://community.ifs.com/topic/new?type=idea to create an enhancement request in IFS Community.
Populate 'assyst' in the Product area and the Tags fields before saving.

Thank you for the reply; I knew about the possibility to verify / restrict data in non-system-fields; it’s a pity this is not possible to apply on system-fields.