One of my clients would like to add additional HTML attributes for SEO purposes as well as to keep line breaks after saving a CMS block or page in the Magento Admin.
Solution:
To do that, you must open the file js/mage/adminhtml/wysiwyg/tiny_mce/setup.js and locate the line below:
var settings = {
Right after the code plugins : plugins,
add the lines highlighted in grey:
var settings = { mode : (mode != undefined ? mode : 'none'), elements : this.id, theme : 'advanced', plugins : plugins, forced_root_block: false, extended_valid_elements: '+ul[*],+li[*],+p[*],+span[*],+div[*],+a[*]', remove_linebreaks : false, theme_advanced_buttons1 : magentoPlugins ...
Save the file and clear your cache to apply the changes.