I can understand you not wanting to change the current behaviour, but can you at least add two checkbox options to get this behaviour (or one if you don’t want to separate them). Just to clarify what I’m after:
1) When on first/last line, pressing Up/Down cursor key will move to start/end of document. This is useful so you don’t have to switch from cusor keys for navigation, plus your suggestion of using Home/End keys is not always feasible when using a laptop which sometimes don’t have these keys.
2) Using Left/Right Cursor arrows or clicking with left mouse on editor area will set the horizontal insertion positon (eg. character 50). Inserting a character, pasting text or using Up/Down cursor keys never changes horizontal insertion position (even when cusor moved to start/end after Up/Down cursor pressed on first/last line). For example, if cursor is on first line at character position 19 and I press right cursor key, the cursor and horiz insertion position changes to character 20. Pressing Up cursor moves cursor to start, but pressing down moves cursor to line 2 and horiz position 20 or end of line (whichever is less). Pressing Up cursor move curor back to first line and it’s also on horiz position 20.
Above behaviour (1) is useful for navigation so you don’t have to move fingers off cursor keys, and some laptops don’t include Home/End keys as well. Above behaviour (2) is useful as you sometimes want to insert different text at same horizontal position on different lines. It allows you to simply type/paste, move cursor up/down and type/paste again, repeat as many times as you need.