margins of a highlighted line

[cichlasoma]

For some filetypes, the current line highlighting strip has dashed margins, for others, it does not. Where can I set it, please?

[alex]

This depends from Current Line Frame style. Tools->Options->Syntax Settings->{Your Syntax}->Fonts and Colors.
If item foreground set to Transparent, frame dashed line is not drawn.
As example check Plain Text settings.

[cichlasoma]

alex: Great! Thanks!