According to the instructions, the number is limited to 10.

-----

Vertical Timeline Object. How to create a timeline

...

• Repeat these steps for all the stages by proceeding chronologically: from the oldest to the newest or vice versa. You can add up to 10 boxes. 

>> https://guide.websitex5.com/en/support/solutions/articles/44001975358

-----

If the timeline could also be created with HTML and CSS code in the HTML object, then the number of boxes would be higher. Here I have instructions in German (with Google translate).

>> https://findelinks.de/123shop-hosteurope/timeline-mit-html-und-css.html (in German)

Otherwise, wait for the Incomedia employees to see if they know a trick or can offer an alternative.

otherwise you can try with some code

https://giancawordpress.altervista.org/vertical-timeline-2.html

I didn't buy the item myself and therefore can't test it.

You could place the objects several times one below the other and set the top and bottom margins to 0 so that there is as little distance as possible between the objects.

Then you could use the maximum number of 10 boxes several times and get 10, 20, 30 or more boxes among each other.