Dunno if anyone's using this code but just in case - I've found and fixed a couple of problems to do with the last_line thing I had recently added but not tested much. Also, in step_thru_goback_history I've added an F7 key that toggles between goback through the "last_line" or "line" where "line" is the centre line of a "chunk" and last_line was the line the cursor was last on in that chunk. If you've enabled def_goback_persistent_history then it's best to delete goback.dat from your config folder before loading the new file coz the previous version didn't include the "last_line" value in goback.dat but the new version expects it to be there (don't really have time to handle this nicely at present).
The zip file includes the latest GFileman toolbar code which fixes a small number of things. GFileman.e has the timer function GFileman_timer_callback() which calls GFH_maintain_line_buffer_goback_history(), so to use the goback mechanism you need to load both GFileman.e and GFilemanGoback.e or add you own timer code to GFilemanGoback.e.
Graeme
P.S. HS2, thanks, I'm alive but not kicking yet so dunno when I'll be back here regularly!