Codemirror’s code is maintained here Suggest new features there.
You argument is counter intuituve. It seems you have not done any research on how codemirror works before suggesting replacing it.
CodeMirror is a code-editor component that can be embedded in Web pages. The core library provides only the editor component, no accompanying buttons, auto-completion, or other IDE functionality. It does provide a rich API on top of which such functionality can be straightforwardly implemented. See the addons included in the distribution, and 3rd party packages on npm, for reusable implementations of extra features.
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On the other hand, CyberPanel is opensource you can view the source code on github and suggest new features through pull requests if you have the ability or clone the project and customise it for your own needs or just start a poll here suggesting new features to the community.
If you have found any vulnerabilities or issues that are breaking the functionality of codemirror in cyberpanel you are free to report them here.