Welcome to the forum @Ser-Bul .
I have some questions and opinions please, so your posting get's even clearer:
a) Which browser and version do you use?
(If you tired sevveral tried several browsers please mention them also.)
b) Which CryptPad server do you use? I suppose cryptpad.fr ? I ask so that I know the CryptPad version.
Opinion:
An "auto return" a soon as one typed all digits is convenient but may also be disturbing. The users differ. Therefore there also seem to be no standard among the many online services, some do "auto return" and some allow you to edit and correct your last digit / character or to decide when you want to finally send it. Me for example would hate "auto-return". But I don't decide, I'm a user like you ant not part of the CryptPad team.
Opinion:
The enter key should be recognized, true. I will need to try it myself. I support this part of your featrue request.
Please give feedback, thanks :-)