In short, it would be ideal if there were an option to add text beneath the Signature box.
Official response
Lara Proud
You are now able to move the Agent Signature within the reply box. Agents can use the Toggle Signature button in the reply box to insert their signature at their cursor in a different position. This functionality was added as part of Deskpro Release 2023.38: https://support.deskpro.com/en-US/news/posts/deskpro-horizon-release-202338