ngspice now makes good VCD files, you can edit a spice deck (tweak a transistor), run ngspice and do a reload in gtkwave, it's definitely the better way to look at the results

But there's one problem, if you have a syntax error in your spice deck (for example you reference a net that no longer exists) ngspice makes
a 0 length vcd file, hit reload and gtkwave hangs (the window manager does that thing when an x app is dead), no longer responding to anything (it comes back if you make a non-0 file)

I sort of understand what's going on, you are trying to live in a world where VCD files are changing underneath you as simulations are running. but perhaps you could treat a 0 length file differently - in particular don't delete the existing display data and pop a dialog box instead

thanks - Paul