Dear Stas, and GAP-forum,

I guess that, by `GAP editor', you mean a GAP session. In order to
read a file into it, you can issue the command

Read("filename");

In order to save the entire present workspace of your current
GAP-session, enter

SaveWorkSpace("filename");

Then, when you want to restore GAP with this workspace, type

gap -L filename

at your shell prompt. I don't know how this works in Windows, though.

Anyway, saving the entire workspace is often not what you want. If you
just want to save the commands that you're entering, issue

LogTo("filename");