There are options the node-red settings.js you can use to disable/inhibit core nodes. e.g.
nodesExcludes:['90-exec.js','28-tail.js','10-file.js','23-watch.js'],
Also see:
- Select which nodes to show in interface - #5 by dceejay
- Remove 'tail' node from node-red
- Can I completely remove a node from the editor? - #12 by knolleary
For themes, there are lots floating around. This repository has several themes where you could get an idea from.
There is also this old theme flowforge/flowforge-nr-theme which adds menu items and sets hyperlinks etc. See this file where the favicon is updated and menu items are added to node-red. You could add as many features to the frontend as you need.
Lastly, there are plugins where you could add features to both the backend (node-red core) and the editor ui. For example this plugin adds a button to the nodes editor. This plugin adds a sidebar next to the debug sidebar.
