I want to add the “anchor to page” command to the anchor menu, but I cannot find the anchor menu in any tab of the customize settings window.
That menu is not customizable. If you need, you can add the command to other menus / toolbars. (But note, that it was removed from the most visible places in UI in tdf#135836, because usually, when people use this anchoring, they are confused, and other anchoring and positioning modes would most likely fit their needs better.)
Yeah, it doesn’t seem to be possible to lock anchors, which makes them seem terrible to me. Anchor to page is what I always want. I guess I’ll add it to the standard toolbar then heh.
It is unclear what “lock anchors” might mean; but please use what fits you best…
I think you confuse anchor and desired position. This is very frequent with people discovering frame features. But I must say that official documentation does not emphasise enough the differences and specificities of anchor modes.
To page means your frame (or image) is irremediably attached to a physical page, no matter what happens to your text. Most of the time, your frame is related to some bit of your text (a paragraph or word) and must remain in its “vicinity”. This is done with anchor To Paragraph or To character.
The effect of the anchor is simply to determine on which page th frame will appear. With To page, this page is fixed (with side-effects unanticipated by casual users). With To paragraph and To character, the page is the same as the paragraph or character and follows it during edits.
Position parameters are then taken into account to send the frame anywhere in the page.
Rather than trying to customise some menu, which drives you into some form of direct formatting, create a custom frame style with all your desired settings (even the dreaded To page mode) and apply it to your frame.
CAVEAT! Frames are extremely sensitive to direct formatting, even seemingly innocent moving or resizing with the mouse). Any direct formatting will ruin the automatic repositioning you have configured relative to your chosen reference. Using frames (or images) in a document requires deep study of the feature and understanding of frame styles to achieve stable predictable deterministic result.