Can I plug a 3 plug extension cord into a 6 plug extender that is plugged into a wall outlet

I have a wall outlet with a 6 plug extender (grounded) mounted to the outlet. It uses ONE of the outlets (the other one is covered by the extender). I have some LED lights at the back of my office and want to run an extension cord with a 3 plug outlet to power the LED’s. All connected devices will not exceed 800W - I have a computer and some monitors connected. It is safe to run a setup this way?

There are multiple concerns with non-temporary use of extension cords, outlet "expanders", etc.:

So there is nothing inherently wrong with an extension cord into an expander, etc. But you need to be aware of the safety issues with physical placement of extension cords, making sure everything is connected properly and securely and, most of all, making sure that the circuit is never overloaded.