I created a LV Plugin from the Plugin SDK specifically the asciioneshot example. The created plugin was registering with DIAdem but not with the local DataFinder. For example the installer for plugin *.xyz is run. Afterword in DIAdem 2018 (64-bit only) you will be able to drag an xyz file into the Data Portal and the file will be loaded via the plugin into DIAdem. Also the plugin will be seen in the DIAdem's Settings -> Extensions -> Plugins list. But using the External Data window your xyz file will not show up because it did not register with the local DataFinder. The root cause of this is that the local data finder is 32-bit and DIAdem is 64-bit.
You need to create both 32-bit and 64-bit versions of the LabVIEW plugin to get the expected functionality of the plugin in DIAdem.
I did this by opening the example Dataplugins\oneshotascii project in both 32-bit and 64-bit to make sure that the correct version of Register LabVIEW DataPlugin.exe was in each project. I updated both projects to be independent by making sure dll names, ini, and build locations where different but with the same *.xyz extension. Perhaps you can leave some items common but I just wanted to be sure that they would install.
There is no error message when trying to register a 64-bit plugin with the 32-bit DataFinder it is just ignored and DataFinder config does not show the 64-bit plugins. Maybe this might help someone trying to develop their first LVDataPlugin.