Extending an extended partition with following unallocated disk space

There seem to be many scenarios, I read quite a few, but I caould not find a match for my problem.

I have this gparted view on my system:
gparted screen

I had sda6 swap sit right behind sda5; I moved that sawp space to another disk. Then swapoff and deleted sda6; then extended sda5 to consume the free 8GB… all good so far.
These two (sda 5 and sda6) were in the same “extended” partition.

However, allocating the unallocated 256 GB does not work; as I cannot extended the sda3 partition.
My understanding is that the 0.25 version of gparted allows for online disk extending.
What options do I have?
Can this be done on a live system?

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Author: MaxG