Thank you for your comments. Pasting the full name in the OPEN dialog, works, under WIN10.
1. so named 'dynamic' 3D plots remain 'static' only
2. in the book I mentioned, the links to the .mws files are embedded in .pdf's. So I will not be able to work with it as expected, as I cannot 'paste filenames'.
3.even from the description in the webshop, it was clear that it's not possible to edit the .mws-files with PLAYER (no wonder - that would mean giving away a full license...), but I expected change parameters, and execute (From @acer's remarks I conclude that the author of the worksheet possibly could provide that by his design)
4. taking looks on documents is a matter of a thousand other software tools, browsers etc
So, the PLAYER seems to be useless for this purpose.... - a question to product management !?
REM: I should have mentioned before - according to the author, the .mws fils were produced with MAPLE15