what is a "list tab", and why can't I edit it?

[eNG1Ne]

Shift + F1 reveals some interesting information about my list styles,
especially when they change from day to day <g> But what is a list tab? and
why can't I set it? when I need to change the value of this tab-setting to
restore the required lay-out, all I can do is add a simple tab.

 

[Stefan Blom]

It is a tab stop set in a multilevel (outline-numbered) list. You can edit
the tab stop position by editing the properties for (the relevant level of)
the list style.