From the Council, I received a description of the regulator for resistance soldering irons, which can normally be bought for a price of up to 100Sk (in Košice at the T. store for only 57Sk!). These soldering irons are powered directly from the 230V network, but they overheat a lot. I have been using a different power regulation method for this soldering iron for a long time.
These soldering irons are sold with a power of 40W (sometimes even 30W). I controlled such a small power in two stages through a rectifier diode. The main switch switches the AC voltage 230V. It is followed by the KY130/600 rectifier diode, which reduces the power consumption to about half, and therefore the soldering iron does not overheat. Parallel to it, there is another switch that bridges it, if full power is needed when soldering larger surfaces, or when the soldering iron is initially switched on.
This switch could be a foot switch, which would make the work easier and faster, unlike manual switching. The diode should be sized for a voltage of 230V and a current of 200mA. There is a 0.25A fuse before the entire electrical connection. A fuse with a resistor can be connected in parallel to it. If the fuse blows, the fuse will light up. This wiring is for beginners (like me) it is generally more suitable than others that are more complicated.