Is it safe to daisy-chain power bars (power strips)?
Yes but only if the total power drawn is less than the rated capacity of the source and the ratings of the power bars.

So you cannot exceed the power rating of source, bar 1 or bar 2.

I thought this was worth a diagram:



I assumed 15A just as an example, respect the ratings and regulations for your locality. I also assumed all bars and source are rated at 15A...

If bar 1 is only rated at 10A then that is the limit so the bottom 3 examples will have to change so that the bar 2 uses less...