That helps a lot, @ErichStyger . Changing heap_1.c to heap_4.c and setting the configFRTOS_MEMORY_SCHEME macro to 4:

It is logical: if the tasks are not going to be deleted there is no need for heap_1 to know the addresses of each block. However, heap_4 must know them, in case memory has to be freed. In fact, in the two images it can be seen that with heap_4 more heap has been used; I suppose that, precisely, it is due to the information stored about the memory blocks.
I have to admit, Erich, that I am a bit embarrassed. I must have read that mcuoneclipse page at least a dozen times, but I couldn't remember that detail. I think, anyway, that it would cost nothing to include those details in the "MCUXpresso IDE FreeRTOS
Debug Guide "- just because it's logical doesn't mean it's obvious.
Thank you very much, once again, Erich.
Asier.