Is it just selection tool that can drawing 2 seconds rectangles?

For now, yes. It's currently in development, so no promises that it'll be stable or functional, but I'm open to any suggestions or feedback!

I have installed the mod, loaded current game, saved the game, loaded the game again and got this:
Error while running event ShowMe::on_player_joined_game (ID 43)
Gui element with name showme-name-frame already present in the parent element.
stack traceback:
ShowMe/control.lua:11: in function <ShowMe/control.lua:9>
stack traceback:
[C]: in function 'add'
ShowMe/control.lua:11: in function <ShowMe/control.lua:9

@Dragonling This should be fixed in version 1.5, sorry for the inconvenience.

thank you!