Gitlab15.1 delete source branch Not configurable?

I installed 15.1, I found that delete source branch is enabled by default when merging code, but I want to cancel this configuration, I can’t find a global option, can I only cancel one project at a time?

From what I can tell, this is only on a per-project setting. I looked back through several versions of archived documentation and was unable to find any mention of a global setting for that checkbox.
I would recommend submitting this as a feature request here: Tracking Bugs and Feature Requests | GitLab