Modifying Tooltip and Legend doesn't work at all

[xnemect1]

Hello,

I am working on diagram of type 'scatter', what I want to achieve is to have pinpoint images on X-axis (datetime) which represent operation or consultation.
This is how it currently looks like:

I am trying to hide legend and modify tooltip to change what is displayed when I hover over datapoint, but I did changes based on ApexCharts documentation but nothing really happened.

This is my code:
constructor() { this.chartOptions = { series: [{// my data], chart: { height: 100, type: 'scatter', animations: { enabled: false, }, zoom: { enabled: false, }, toolbar: { show: false, }, background: 'white', }, legend: { show: false, }, tooltip: { custom: function ({ series, seriesIndex, dataPointIndex, w }) { return '<div>Hello World!</div>'; }, }, ...

Can anyone help me please what can be the cause why it is not working and if it can be fixed?
Thanks in advance for your advices.