Install libqscintilla2-qt4-designer-dbg by entering the following commands in the terminal:
sudo apt update sudo apt install libqscintilla2-qt4-designer-dbg
Description:
Qt4 Designer plugin for QScintilla 2 (debug)
QScintilla is a text editor for Qt4 with features especially useful when writing and debugging source code. These include support for syntax styling, error indicators, code completion, call tips and margins. . Styling choices are more open than with many editors, allowing the use of proportional fonts, bold and italics, multiple foreground and background colours and multiple fonts. . This package contains the debug extensions for the QScintilla 2 widget in the Qt4 UI Designer.
Homepage: http://www.riverbankcomputing.co.uk/software/qscintilla
Version: 2.10.2+dfsg-4
Section: universe/debug