How to use a DLL from another folder than <Geosoft>\bin

The old and new GX developer documentation specifies a way to locate DLLs not placed in <geosoft>\bin directory: one may add a registry key, and then populate it with the names of each subjected DLL.

I haven't been successful so far, not in older OM versions nor in 9.9. Can anybody share with me what exactly needs to be done? A very simple example (similar to the one I tried below) would suffice.

This is what I tried:
1. I compiled XToolControl project (obtained XToolControl.dll and copied into 

    C:\Program Files\Geosoft\UserDLLs\XToolControl.dll

2. I followed "Installing your custom DLL" (e.g. https://geosoftgxdev.atlassian.net/wiki/spaces/GXD99/pages/1525973535/C+C+Development) and created the following registry key (while one may import from a .reg file):

[HKEY_LOCAL_MACHINE\SOFTWARE\Geosoft\Oasis montaj\3rdPartyDLLs]
"XToolControl.dll"="C:\\Program Files\\Geosoft\\UserDLLs\\XToolControl.dll"
 
3. I created a user menu with the following content:

    MENU "&OM_TOOLS"
    ITEM  "XToolControl ..."   ,XToolControl.dll(TestXToolControl.ShowXToolControl;Show)

4. I loaded OM_TOOLS menu but I got no item shown

5. when I moved XToolControl.dll int <Geosoft>\bin folder, it worked fine

Thank you very much,
Dumitru