The idea is to only show "Don't know" and "Refuse" answer option if respondent attempts to skip a question. This, as I imagine, would require (a) making the question mandatory, (b) hiding certain answer options, (c) revealing hidden option on an attempt to skip, altogether with a warning message.

Obviously, this would require some Javascript magic to hide the options and then wait for the trigger to reveal them. While I find examples of hiding certain elements of questions, still can't locate an example of accessing the trigger for the "Mandatory" message to use it further in the desired scenario.

Any ideas are very much appreciated

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Sample scenario:

State 1:

Question? * (mandatory)
1. Yes
2. No

Action: attempt to [Next] w/o selecting any option

State 2:

Question? * (Warning message)
1. Yes
2. No
3. Don't know

Have a look at this thread for detecting a mandatory error - forums.limesurvey.org/forum/can-i-do-thi...-after-submit#204288

Thanks for a hint! This definitely looks like a great starting point to build the solution further.