To insert special characters in blocks such as #$%&*(){}[] you need to use the & hex code format (full list at >>  https://dev.w3.org/html5/html-author/charref)

To insert markup / HTML in blocks description and content just use single quotes, like <a href=’YOURLINK’>your text</a>


Blocks availability matrix

 

Posts

Pages

Campaigns

ArticlesBy defaultXX
Carousel Header XX
Columns / Tasks XX
Cookies XX
CounterXXX
Covers XX (only “Content” style)
Engaging Networks Form XX
GalleryXXX
Happy Point XX
Media  X (Embeds only) XX
Social Media X (Embeds only)XX
Split Two Columns X 
Spreadsheet / TableXXX
Submenu X 
Sub PagesX
Take Action BoxoutX (in Post Element fields)X 
TimelineXXX

Blocks menu in Gutenberg

In the content field, there is a small arrow inside a circle – click on that element to add a new block. A pop up window will open and you now have several options to choose from: