What is the vertical line in the editor screen for?

[TheInsider]

I've got my ThinAir editor theme set up pretty much how I like it, except for that line. At the 92th character position, there is a thin vertical line. What is that meant to indicate, and can it be disabled or changed? I've searched the forums, docs, etc but find no reference to it. (Probably because I don't know what it's called. )

[ErosOlmi]

Yes you are right, thinBasic has so much options all to be documented.
Step by step, sooner or later ...

All thinAir themes are derived from Default theme.
Check inside any theme xml file and you will see the following line at the beginning:

<ThinAirTheme version = "1" parent = "Default.theme.xml">

So when thinAir apply a theme, first of all it will apply "Default.theme.xml" theme and then it will apply the specific options inside your theme
"Default.theme.xml" (and other thinAir official themes) will be overwritten at every thinBasic install so never change it

That said, to change some behavior, just copy the option you want to change from "Default.theme.xml" into your personal theme and make some changes

In this case copy from "Default.theme.xml" the following node into you theme

<options name = "edge"> <!-- You can choose to mark lines that exceed a given length by drawing a vertical line or by colouring the background of characters that exceed the set length. -->
    <item name = "mode">1</item> <!-- 0=none, 1=line, 2=background, 3=multiline -->
   <item name = "column">90</item>
  <item name = "color">230,230,230</item>
</options>

and change

<item name = "mode">1</item>

to

<item name = "mode">0</item>

Important: XML files are case sensitive

[TheInsider]

Excellent! That actually answers the other question about themes I had. Two for one there!