[Question] Define or hide properties for specific components

I'm not sure if this is the optimal way of doing it but you can listen to the event component:selected and if the component selected is the one you want you can add a new sector. Then you need to listen to the event component:deselected and if the component deselected is the one from before you remove the extra sector. If you don't want to create a whole sector you can juts use addProperty and removeProperty over an existing sector. The same can be done to remove sectors for a specific component.

editor.on('component:selected', function(component) {
  if(component.attributes.tagName == 'div') {
    const styleManager = editor.StyleManager;
    styleManager.addSector('div-only-sector',{
      name: 'Div only sector',
      open: true,
      properties: [{ name: 'This is a div'}]
    });
  }
});
editor.on('component:deselected', function(component) {
  if(component.attributes.tagName == 'div') {
    const styleManager = editor.StyleManager;
    styleManager.removeSector('div-only-sector');
  }
})

Actually, you can also rely on a few Component's properties made exactly for this purpose:

• stylable - True if it's possible to style the component. You can also indicate an array of CSS properties which is possible to style, eg. ['color', 'width'], all other properties will be hidden from the style manager. Default: true
• unstylable - Indicate an array of style properties which should be hidden from the style manager. Default: []
• stylable-require - Indicate an array of style properties to show up in Style Manager which have been marked as toRequire. Default: []

About the stylable-require, it works when you configure your Style Manager with some property containing toRequire options, so it will be hidden until some component will not require it. Eg.

{
      name: 'Dimension',
      open: false,
	  // use buildProps to create built-in properties
      buildProps: [ 'width', 'flex-width', 'height', 'max-width', 'min-height'],
	  // flex-width doesn't actually exist, so extend it in properties via `id`
      properties: [{
        id: 'flex-width',
        type: 'integer',
        name: 'Width to req',
        units: ['px', '%'],
        property: 'flex-basis',
		// This will hide the property and will be shown only if some 
		// selected component would have something like: 
		// 'stylable-require': ['flex-basis']
        toRequire: 1,
      }]
    }

@peakrams the warning is actually there but the Github's Markdown doesn't let you apply custom styles to make it more visible ¯\_(ツ)_/¯