How can I have Bitcoind.exe use the core data from Bitcoin-QT on my D drive. Using Windows 10
There are a few ways to do it one of which is modifying the shortcut as you've mentioned.

The easiest way is to create a bitcoin.conf file in %APPDATA%\Bitcoin. That's the default directory bitcoind will look for a configuration file.

Based on your question you can set the contents of bitcoin.conf to:

datadir=D:\Bitcoin Core data