Another by the way.
At first time I have try to make empty plugin, I think mistake was that I have used 'valentina_serials' everywhere except class name
class plgHikaserialValentina extends hikaserialPlugin {
And this small mistake, makes plugin to be not workable. Joomla have installed it with success, but
a) plugin was not shown in Joomla's list of plugins.
b) plugin was listed by HikaSerial in its own list of plugins, but
c) if you enter into plugin, there was no buttons on top to make NEW, for example.
The most nice thing that was ZERO errors and warnings from both Joomla and HikaSerial...
Sounds like a thing to improve, yes guys?
When I have made everywhere only 'valentina', then plugin was correctly installed and listed.