GnuPG - Expiration (Subkeys)

I have several GnuPG keys which I edited with KGpg.
https://apps.kde.org/de/kgpg/

Unfortunately, the subkeys were not taken into account when setting the expiry date.
How can I retroactively edit my expired keys and expire also the subkeys?

Hello,

try Kleopatra, that should set the expiration date on all subkeys.
If this does not work, the command line offers more expert options,
using
gpg --edit-key

Regards,
Bernhard

I don’t want to change the existing expiration date.
So renewing the keys is not an option.

How can I force changing the expiration date?

Open the Certificate details, go to “More Details” to view the subkeys and then right click them to get the option to change the expiration date.

IIRC, you can set the same expiration date, but this time make sure to include all keys.