It is a key functionality in the process of signing the procedures.
The preferred signatory is considered the first choice to sign a procedure. However, if someone else has signature permission, they will be able to sign the document even if they are not the preferred signatory. If it is not assigned, you can select it when you send to sign a procedure.
When you activate this option, the Send to sign information box will appear, where you can select the preferred signer or continue processing without selecting him. On the other hand, if you do not activate this option, the information box will not appear when you send a procedure to be signed.
If you check the option do not show again , this information box will not appear again.