How to add a mix of text and numbers to a slider?

Use Mutation Observer for this or you can also take help from this post

Hi daanoo ,
You can achieve the above functionality shown in your link by adding below code in your Qualtrics JS API:
Qualtrics.SurveyEngine.addOnload(function()
{
/*Place your JavaScript here to run when the page loads*/

});

Qualtrics.SurveyEngine.addOnReady(function()
{
/*Place your JavaScript here to run when the page is fully displayed*/
// Select the node that will be observed for mutations
const targetNode = document.getElementsByClassName("sliderToolTipBox")[0];
let observer = new MutationObserver(function() {

if(targetNode.innerHTML=="0")
{targetNode.innerHTML ="Hello";}
else{
targetNode.innerHTML =Math.abs(targetNode.innerHTML);}
observer.disconnect(); // turn observer off;
observer.observe(targetNode, {
 attributes: true,
 childList: true, // observe direct children
 subtree: true, // and lower descendants too
 characterDataOldValue: true // pass old data to callback
});// turn back on

});

// observe everything except attributes
observer.observe(targetNode, {
 attributes: true,
 childList: true, // observe direct children
 subtree: true, // and lower descendants too
 characterDataOldValue: true // pass old data to callback

});

});

Qualtrics.SurveyEngine.addOnUnload(function()
{
/*Place your JavaScript here to run when the page is unloaded*/

});

Hope it resolves your query😊!!!