Limit Choices in Multiple Select

Too eager to celebrate were we. :-)
It appears that the variables are being shared across the questions and hence this will only work for the last question in which code is inserted. To make it work for all, you'll need to rename the variables (

qid

,

that

,

okay_choices

) for each question. You can change them to anything like (

qid1

,

qid2

,

qid3 

etc.) Just make sure, they are unique for each question. Here's how it should look finally:
Qualtrics.SurveyEngine.addOnReady(function(){
    const qid1 = this.questionId;
    var okay_choices1 = [];
    
    that1 = this;
    this.questionclick = function(){
        sel_choices = that1.getSelectedChoices();
        // Set the maximum number of choices you want here
        if(sel_choices.length <=3){
            okay_choices1 = sel_choices;
        }
        else{
            alert("You can not select more than 3 choices.\\nPlease deselect to select another.");
            sel_choices.forEach((item) => {
                Qualtrics.SurveyEngine.registry[qid1].setChoiceValue(item,false);
                });
            okay_choices1.forEach((item) => {
                Qualtrics.SurveyEngine.registry[qid1].setChoiceValue(item,true);
                });
        }


    }
   
});