The button for a certificate in the list prompts a new certificate to be created with a new validity period.
In the case of a simple certificate, select the new period under Validity and enter the CA Password of the relevant CA certificate. For certificates that are not self-signed, a completely different CA can be selected when renewing. This is not limited to the current CA. For certificates that are not self-signed, two passwords must be entered; the CA password and the private-key password of the certificate being renewed.
With a Certificate Authority (CA) you can also change the Common Name and assign a new validity period to the certificates signed by this CA.
Use the buttons at the bottom right in the editing box to renew the validity period of the selected certificate or CA and, if necessary, the certificates signed by it, or to cancel the dialog (Cancel).