Another plus for the incandescent light bulbs.
When such light bulbs are cold, they have a relatively low resistance, and stay mostly off, even when in series with a load. However when the current increases, the bulb heats up, which inreases it's resistance more, etc.
So in effect it acts as a self repairing fuse a bit like to a PPTC. When they're cold, they can conduct more current than their nominal current when the light is on, and they have a pretty obvious "tripped" indication that is hard to miss.
Ideally you put a few of such lights (with different wattages) in a box and add some switches, to adjust it to the job you're working on.
This video from Photoninduction with a 20kW lightbulb clearly shows the resistance difference between hot and cold.
The idea of a variac also used to work, but there is a catch with SMPS circuits. These can draw too much current when input voltage is too low and this can result in fuses of the SMPS itself blowing.
Isolation transformers are also very robust. It's a chunk of steel and a bunch of copper wire, and they do not get damaged quickly by moderate overloads. The primary failure mode is the thing gets so hot that the wire insulation gets compromised, and it takes time to overheat. (Although, when the secondary has a hard short, it's pulled into severe saturation, which leads to a massive overload of the primary coil.)
If you want to go fancy, you can add a current transformer or such an HALL-effect current sensor and a microcontroller, and then write a bit of software to make an adjustable cut off, both for "instant current" and I-squared-t. and then switch a beefy SCR or solid state relay.
Another luxury option is to use a PKZ:
https://duckduckgo.com/?q=pkz+motor&t=hx&va=g&iar=images&iax=images&ia=imagesThese give protection against both "instantaneous high currents" and slow overloads with an integrated bi-metal.
There are also household variants of these, but the PKZ is usually adjustable, while the household versions have some fixed current limit.