Draw a polygon with a lot of points in Draw or Impress. Switch to point edit mode. You should get the "Edit Points Bar", if not you can enable it in menu View. This toolbar has on the right side an icon for the command .uno:BezierEliminatePoints with tooltip "Eliminate Points". Open the help text for it, e.g. by search for "Eliminate Points". The text is totally wrong and does not describe the feature. Especially these parts in the help are nonsense: "Marks the current point or the selected points for deletion." --> The tool does not "mark" anything. --> The tool does not work on selected points (plural!) "If you convert a curve or a polygon with the Convert to Curve icon into a straight line or ..., it is removed." --> The tool "Convert to Curve" is unrelated. The help text is identical to the text in StarOffice 5.2, beside the inaccuracies, which slipped in by translations from German to English. Actually this tool enables a mode where you can interactively delete a point in a polyline or polygon by dragging the point with the mouse. Look video https://www.youtube.com/watch?v=QuQSZSCOtAY, around 13:03
I ask Armin Le Grand how the tool "Eliminate Points" works. The answer is in German, but it is still useful. "Ich denke, der Knackpunkt ist, dass wohl nicht klar genug wird, dass es sich bei dem Kommando in der Toolbar um das interaktive Punkte-löschen handelt. Natürlich kann man ohne dieses Kommando/Button jederzeit Punkte des Polygons selektieren (Tastatur, Maus,...) und mittels DEL löschen. Der interaktive Modus, der mittels des Icons aktiviert wird, arbeitet etwas anders: Bis zu dessen Deaktivierung (ins Leere klicken) kann man jetzt einen Punkt des Polygons greifen und bewegen. Es wird eine interaktive preview gezeigt. Wenn der Punkt in einem gewissen Grenzbereich nahe genug an die gedachte Gerade zwischen seinem Vor- und Nachfolgepunkt gerät, 'schnappt' der bewegte Punkt auf diese Linie. Wenn man jetzt die Maustaste loslässt, wird dieser Punkt gelöscht. Das ist ein alter, interaktiver Löschmodus, der aber durchaus intuitiv und gut funktioniert. Ausserdem eine der unglaublich vielen Dinge, wenn man die Interaktionen umstellt, zuletzt auf Overlay und Primitive. Zu den Kurven: wirklich intuitiv arbeitet der Modus natürlich nur, wenn nicht mit einer Kurve gearbeitet wird. Natürlich kann ein polygon gemischt sein, d.h. bestimmte Kanten sind kurve, bestimmte nicht. Es ist also nicht sinnvoll, diesen Modus für polygone, die Kurvenabschnitte enthalten, einfach zu deaktivieren. So, hoffe geholfen zu haben. Eventuell sollte man den Modus einfach umbenennen, das 'interaktiv' sollte vielleicht mit rein. Ein weiteres Beispiel für eine gute Funktion, die unklar und schlecht angeboten wird." "Also: Ich denke, man sollte es komplett durch eine aktuellere Beschreibung des interaktiven Modus ersetzten, möglichst ohne mehrdeutigkeiten."
@Olivier: I reading my really old unread german de-discuss mails. At the German translation we removed many parts. Best is to do this at the English help, too. See short discussion in German at http://go.mail-archive.com/PcPDtyCQeJNNaZi8GIb-cVGhp_4=
Bug #130024 deals with similar issues. To relieve possible problems because of the german text I offer a new help text based on the german statement by Armin LeGrand. My proposition for a new help text: This seems to applicable only to polygon shapes. If you switch on this mode, then you can eliminate points by dragging them near to the imaginary straight line between its two neighbouring points. Phantom lines from the point you drag to its neighbours are shown while the point is dragged, and these snap into one straight line if the point is dragged sufficiently near to this line. If you then release the mouse button, then the point will be deleted. The mode will be still active, hence you can eliminate other points, if you wish to. Leave this mode by again clicking on the symbol.
"sufficiently near" is determined by the angle in Tools > Options > Draw > Grid > Constrain Objects > Point reduction. But I don't know the exact way. For straight line segments this option conflicts with the insert point, because the inserted point will be deleted immediately, if near enough to the line. And because the instruction for insert contains "move a little bit" that likely happens. The proposed description is better than the current one. That section in the help should be improved together with bug 130024.
Based on Regina's statements in the previous comment and additional information provided by her I propose the following amended help text: This seems to applicable only to polygon shapes. If you switch on this mode, then you can eliminate points by dragging them near to the imaginary straight line between its two neighbouring points. Phantom lines from the dragged point to its neighbours are shown while dragging, and these snap into one straight line if the point is dragged sufficiently near to this line. If you then release the mouse button, then the point will be deleted. "Sufficiently near" is determined by the parameter "Point reduction" in Tools -> Options... -> LibreOffice Draw -> Grid: if the sum of the angles between the lines from the dragged point to his neighbours and the line connecting the neighbours is less than this parameter then the point will be eliminated. Eqivalently: when the difference of 180° and the angle between the lines from the dragged point to his neighbours is less than this parameter, then the point will be eliminated. The mode stays active, hence you can eliminate other points, if you wish to. Leave this mode by again clicking on the symbol. Make sure the mode is inactive, if you want to add point to a straight line, because otherwise the point will very probably vanish as soon as it is created.