How to create a desktop menu entry manually in Linux

This is kind of an odd thing to be posting about nowadays with Linux desktops mostly including a menu editor or installable third party packages like menulibre and alacarte being able to achieve the same outcome. However, LXQt does not include a menu editor that is comparable to the above options, and whilst both of the above can be installed in Lubuntu or Debian/LXQt, the results of running them are confusing. It is possible with PCManFM-Qt file manager to edit applications shortcuts directly in a specific area of the standard user interface but that is confusing and difficult to understand. Fortunately the majority of desktop environments support a standard method of creating shortcuts as .desktop files stored in a standard location.
The .desktop files are created in either of the following locations: /usr/share/applications or ~/.local/share/applications. The difference between these is that the former location is computer based and the latter is user based. For this example we have downloaded Firefox Developer and extracted it from the download file. This does not give us that menu shortcut so we have to create it. Typically we will copy the FFDE files to ~/Applications folder and create a local shortcut in ~/.local/share/applications which has a double advantage at reinstallation time that both the application and its shortcut are located in the user profile and therefore do not need to be reinstalled when the operating system is.
The typical format of the .desktop file looks like the following (in this case the actual parameters used to start Firefox Developer from where we installed it):
[Desktop Entry]
Comment=Firefox Aurora with Developer tools
Exec=/home/patrick/Applications/firefox-dev/firefox %u
Name=Firefox Developer Edition

Some of the above might not be needed.

The key issue, however, is that LXQt (at least on Lubuntu, but probably also on Debian) does not seem to recognise user specific icons as part of its menu. When one was created like the above, it ended up being put into the Other submenu rather than the Internet submenu. Likewise one could be created with menulibre and would be created in the same location by default (~/.local/share/applications) but ran into the same issue that LXQt would push it into the Other section of the menu. I am still experimenting to see how this can be overcome but for now, either method is possible but if both are creating the same outcome then using menulibre is obviously preferred as a GUI.