@walter.annaert : As shown in the initial post by @lemuba you need two things:
a) A slider to input the desired charge current (which you now have)
b) An automation that triggers on the slider (changes) and sends a command to the wallbox (see the post).
But maybe your question is: how do I automatically start / stop charging?
For this there are multiple integrations. The one that I use is EV Smart Charging which is available under HACS. It uses ‘dynamic pricing’ to find the moment of lowest electricity prices to charge the EV.
If you want to see how I used this, look at the post EV Smart charging with dynamic energy prices in the EU - Energy - Home Assistant Community
There are also Integrations that work with solor panels and home batteries. I have no experience with those.