Hactar Editor
Hactar editor can be used for almost any SGF editing purposes, including to record games, create problems or comment games.
Modes
Editor is always in one of modes: View
, Record 
, Markup 
, Setup 
or Scoring
.
Record
Icons in edit window:
Delete move. Deletes last visible played move.
Undo edit. Undo last change.
Numbered Moves in a Row
Row of numbered moves moves can be used to move around in the game. Letter C with Yeollow background indicates that move has some kind of comment or markup. So it might be worth a look when going thru a game.
Insert Move or Add Variation?
Stones are most often added to the end of the game when recording a game.
When in middle to already recorded moves, it is possible to select between two actions when adding move: add variations 
or insert move 
.
When variation is added, new move is put into a new variation. This way existing recoding of game is not modified.
Inserting move can be used for example to add move that was forgotten when recordign the game.
Ai Analysis
Ai analysis shows evaluation of the next moves in the board.
The biggest number is how much the move loses points compared to the best next move. So in the best move this number is always 0.0, and move is green. Below the point-loss is how many evaluations have been done to get this estimate.
The game progress shows winning-% (0...100%) with red line. Point difference is shown as black-and white background. Both values are also shown textually.