We are still using Sharepoint online classic publishing site.
We enabled unique permissions so that only "Pages Owners" group has full control permission on the Pages library, not on the site level. Somehow the users in the group can create/edit/delete the pages, but they can't either change anything in the existing content editor/Script editor web parts, or see content editor/script editor web parts from the toolbox if they want to add a web part. The custom script is on in classic SharePoint admin settings page and it was never turned off as showing below:
Somehow, if I assign full control permission to the group on the site level, they will start seeing these 2 web parts, but that's a overkill and we don't want to do it. I have no idea what's going on, hope there is an answer for this. Thanks.