The .desktop files work flawlessly when double-clicked. Opera opens, BleachBit opens, etc, no problem there.
What I want, what I need is to get a shortcut in Applications (or, in Windows world, Start) menu when I install an app from a converted ("tazpkg convert" command) DEB or RPM package.
This is obviously a problem with the TazPKG app itself, since it's not a one-package problem. Those .desktop files are generated by TazPKG, but don't "function" properly for some reason. I've edited the opera-browser.desktop file to match the scheme of Midori's and got no result.
Maybe my system IS broken in some way, but how? TazPKG works the same way wether it's a repository package or a converted, local one. At least it should.