This is editable text. You can use @Mentions as well as throw in some tags using prosemirror-mentions.
Trigger @mentions by typing "@" followed by some text. Same with "#" and #hashtags!
To apply styling, you can select a piece of text and manipulate its styling
from the menu. The basic schema supports emphasis,
Block-level structure can be manipulated with key bindings (try ctrl-shift-2 to create a level 2 heading, or enter in an empty textblock to exit the parent block), or through the menu.
Try using the “list” item in the menu to wrap this paragraph in a numbered list.