It is not necessary to show a Cookie consent form. Here is a related excerpt from the EU commission website The EU Internet Handbook:
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Consent is not required if the cookie is:
- used for the sole purpose of carrying out the transmission of a communication, and
- strictly necessary in order for the provider of an information society service explicitly required by the user to provide that service.
- Cookies clearly exempt from consent according to the EU advisory body on data protection- WP29 include:
user‑input cookies (session-id) such as first‑party cookies to keep track of the user's input when filling online forms, shopping carts, etc., for the duration of a session or persistent cookies limited to a few hours in some cases
LimeSurvey is clearly covered by this case – without a cookie, it would not be possible to run a normal online survey safely that spreads over several pages.