Those shown are any that you have the prereq techs for, plus the "starters" for each invisible group (Alph, Bronze and CerBur at first), minus the hidden group. Again, give CIV2PLAN a try. It has both a hidden mode (the default) plus a show-all option, and can save and reload a tech path to a text file. I keep it open in a window whenever I am playing (I tend to start and stop a lot) with a projected path set up about five techs ahead of where I am. If I get a tech in trade or from a hut, I just back it up, insert the new one, then re-examine the next options and replan.