M365 CEWP FAQs (Content Editor Web Part for Modern Experience Sites)
About Simple CEWP
Simple CEWP does the same as its web part for Classic Sites: It allows you to add custom content on a SharePoint modern page for the purpose of adding CSS or Jscript.
Simple CEWP is compaible only with M365 modern pages, so it's support is limited to SharePoint Server 2019 On-Prem and Office 365 (aka SharePoint Online).