User ranges are intended to allow custom formatting over syntax highlighting provided by the TSyntAnalyzer. They may be used without syntactical analyzer. 

User range is a text range from the StartPos to the EndPos that can have style (Style), collapsing capability (Collapsable), top and bottom line separator (LineBreaks). 

You can create user ranges in design time using TCustomSyntaxMemo.UserRanges property (collection) or visually in the property editor for TCustomSyntaxMemo.Lines or in the component editor of TSyntaxMemo ("Edit text..." item in the popup menu). This editor of text content allows text and user ranges editing. 

User range looks for the Style in TSyntStyles.Styles (property UserStyles) and TSyntAnalyzer.Formats is linked to TCustomSyntaxMemo.

TSyntaxMemo Properties