Hi サンデャ 管理者 ,
Sorry for the late reply, I've been working on this for the past few days.
SP 2019 supports custom script by default. Generally, there is no need to apply the above PowerShell command unless you have problems when applying custom codes. So, in SharePoint 2019, there is no GUI /powershell to to disable it. This is by design.
You say you can't test a lot of things, can you tell me exactly what they are and maybe I can find alternatives for you.
Thank you for your understanding and support. Have a nice day!
If the answer is helpful, please click "Accept as Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.