Never noticed where but I would put the Variac after isolation.
With it you will be safe, can turn it down to break in a set &
sniff out weak tubes that wont run on reduced voltage.
Monitoring the current is essential for troubleshooting TV
Hoz & HV circuits in solid state ( SS ) sets.
Going higher is a good test of a SS sets regulator.
You can test things that run on 24 VAC or other low AC
voltages, just dont bump the knob !
73 Zeno
