Shortcut for Indent Row

OO 4.1.4 Preferences Keyboard
If you select Go to Next Cell, how would you Indent row with a shortcut ?
WHat is meant bu inserting a tab character ?

As I explained in your previous post about keyboard shortcuts, Command-] is the shortcut for indenting a row, regardless of this preference.

A tab character is a horizontal space that aligns the next character under the next tabstop. In OmniOutliner 3, there was a ruler that would let you specify custom tabstops. We’ve heard from users who would like this feature restored in OmniOutliner 4.

On my keyboard I need to press Alt ) to get ] so it is not convenient

You can change this shortcut (or any other command that is accessible through the menu) using System Preferences (Keyboard > App Shortcuts). For example, if you wanted to use ⌥+⌘+I to indent, the setup would be as follows:

My OO is not there

Applications do not appear in the list until after you use the plus button to define at least one shortcut for their menus.

To add to what Kyle shared, when you click the + button you’ll be able to select OmniOutliner Pro and type the name of the menu item (make sure it matches the name exactly) and assign a shortcut key.