You can do a repair install of 10, I'm not positive if it will effect your installed program's though.
It will repair the registry.
Personally, I wouldn't begin to do repairs and stuff at this moment. He has the problem, I have the problem, and it seems others have it too (also on this forum). So there is something we have missed, or there is a slight bug...
I will try to make a repair of my windows 10 installation tomorrow and update here with a result.
Thanks you guys for your help in narrowing this issue down
Rerun the office setup, if memory serves me, it will detect its already installed and offer a repair option.
It is mentioned that MS is using a database with a system account to generate that list, and it has a maximum of around ~500 entries.
And here is an MS thread about it