manual should be corrected

not quite, none gets deleted, but only the last 5 are visible.
And I believe you can amed the handbook yourself.

Definitely there shouldn't be incorrect information in the Handbook. But I also think perhaps it is better not to include too much detail about musescore.com in the MuseScore manual, since the details of how musescore.com works can change over time and not necessarily in sync with MuseScore releases. Probably m,akes more sense to document musescore.com *on* musescore.com, and have the Handbook for MuseScore just give basic information that is unlikely to change as musescore.com evolves. Unless Thomas feels otherwise...

Up to now I have been using Gvox "Music Time" program. I find MuseScore is somewhat more difficult to learn (partly because I am familiar with Music Time) and not very intuitive. It seems I always need to have the User Guide open any time I am using Muse Score. Therefore I suggest that you have a "Quick Start" guide or "Quick Reference" showing the basics i.e. simple steps for the most used and essential features. I have gradually built up a file of my own, with the following headings:

Entering Notes, Rests, and Accidentals
MIDI Input
Exit Note Entry mode
Edit Mode
Exit Edit Mode
Insert/add note/chord
Delete note or object:
Move note up/down
Move note left or right
Change value of note
Stems up/down
Insert measure
Delete Measure
Re-size measure
Staff/System spacing
Voices
Triplets/duplets
Tempo
Time/Key Signature
Printing

There are still a few more I could add.