Can I use a light fixture box as a junction box for a Baseboard

I would like to know if it’s allowed to use an octagonal box currently used for a light as a junction box for two baseboard heater ( I need to relocate the current line).

The reason we need to relocate the first baseboard wire is because we are opening our roof to create an access to the future rooftop patio. The main wire was going down to a first thermostat in a wall we are removing and was continuing to a second one we want to keep. In other word, I need to pass this wire on the other side of the hole we are building and we are lacking some lengths unless we create a junction box somewhere. Since we have the light of our living nearby I wanted to use that box instead of creating one in the ceiling for nothing.

Our baseboard are on 220v circuits.

I am able to modify the depth of the octagonal box if needed.

Thanks