Not enough room in live downloads folder; direct /.iso to permanent storage instead ?

It is unclear to me what problem you face. Do you want GRUB to have an entry for a system that would be an ISO on the hard drive?

Not so complex as that. I want to burn an up-to-date Live DVD,
but the iso file is too large to fit on the Live system's downloads
folder. Most downloads give me he option of opening a download or
saving it to a location of my choosing. My local HDD is a HITACHI;
and the system has 8GB of RAM. I have a working WiFi connection.

I'm writing this from the Live version of Trisquel. Still searching
for a working version of the kernel. My ThinkPad is a Lenovo T420,
formerly held in high regard.

So you are trying to download an ISO from a live system because you have no other choice (no functioning installed system), right?

Most downloads give me he option of opening a download or saving it to a location of my choosing.

Indeed. How do you download the ISO? If from a Web browser, you should be able to right click on the link and, in the contextual menu that is displayed, on "Save as". If not, look at the settings of the Web browser and specify there the folder where downloaded files are saved or check the box "Always ask where to save files" or copy the link and use wget in a terminal or... The filesystem on the disk must be mounted before that.