NCH Crescendo does not appear to have a dedicated tool for automatic rhythmic slash notation (notes with slash heads for guitar comping), unlike some other software.
Create Manually
Place notes or rests in the desired rhythm using the Note Toolbox on the left (shortcut: numbers 1-7 for notes, Shift+1-7 for rests).
Right-click a placed note head and look for a notehead shape option in the context menu—manuals mention changing shapes for percussion (e.g., cross/X, diamond), which may include slashes or crosses for guitar rhythms.
If no slash option exists, use X (cross) noteheads as a common substitute for rhythm slashes in guitar parts; add chord symbols above via the Fretboard/Chord Toolbox on the right.
Add Chords
Select a chord symbol from the Fretboard Toolbox, click above the staff to place it—position over your rhythm slashes.
Right-click the chord symbol to edit name, diagram, or display style (name only, diagram only, or both).
Resources
Check the radial menu (ALT + number on selected note) for quick edits, including potential notehead changes.
View video tutorials for chords and tablature, or contact NCH support for slash-specific confirmation.