When you want to use a piece of content several times in a textfield, you can make a Box first and reuse it when needed.
It is a new structure. It acts like a block, but embedded in a text field. You could use it as a piece of information to start or to end with writing articles.
The box entity is just like a block with fields.
Add it to the text formats you want.
Make a box. Use multiple fields if needed.
Add the box like this.