Ok @jetbrains. Got vacation. Time to learn new stuff. Fresh Coffee. On the sofa at the fireside. Download @intellijidea. Unpack. Start. Nice setup. Start LearnProject. Managed Selection section. Now for Comment Line. "Comment out any line with Strg+Schrägstrich". Does not work./2
Keymap may differ on various platforms, for example on mac it is CMD + /, or you could use "Code | Comment with line comment" menu item.