The uno command .uno:InsertBookmark needs to be duplicated as .uno:InsertAnchor for use in Writer Web and as webpages use the word anchor to identify bookmarks.
And then of course change the menu Insert .. too?
Yes the new .uno:InsertAnchor would be included in the Insert menu and in the standard toolbar replacing .uno:InsertBookmark.
Now that Maxim has implemented UNO command aliases in bug 84258, this was a simple fix.
Yousuf Philips committed a patch related to this issue.
It has been pushed to "master":
tdf#87610 Replace Bookmark with Anchor in Writer Web
It will be available in 5.2.0.
The patch should be included in the daily builds available at
http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More
information about daily builds can be found at:
Affected users are encouraged to test the fix and report feedback.