There is a "quick and dirty" way to notate pentuplets if appearance is not a factor. For the first two notes, increase the tempo by a factor of 5/4. Tripletize the last three notes and change the tempo to 2/3 of the new 5/4 tempo. After the end to the pentuplets (triplets), reset to the original tempo. The downside is an unwanted triplet bracket, but the upside is no new notes or rests need to be added to other (non-pentuplet) staves.
Results should be exact if the original tempo is a multiple of 12.
!NoteWorthyComposerClip(2.5,Single)
|Clef|Type:Treble
|TimeSig|Signature:6/4
|Dynamic|Style:ff|Pos:-8
|Tempo|Tempo:84|Pos:7
|Note|Dur:4th|Pos:1
|Note|Dur:4th|Pos:1
|Tempo|Tempo:105|Pos:7|Visibility:Never
|Note|Dur:16th,Accent|Pos:1|Opts:Stem=Down,Beam=First
|Dynamic|Style:p|Pos:-8
|Note|Dur:16th|Pos:1|Opts:Stem=Down,Beam
|Text|Text:"5"|Font:StaffItalic|Pos:-12
|Tempo|Tempo:70|Pos:12|Visibility:Never
|Note|Dur:16th,Triplet=First|Pos:1|Opts:Stem=Down,Beam
|Note|Dur:16th,Triplet|Pos:1|Opts:Stem=Down,Beam
|Note|Dur:16th,Triplet=End|Pos:1|Opts:Stem=Down,Beam=End
|Tempo|Tempo:84|Pos:7|Visibility:Never
|Dynamic|Style:ff|Pos:-8
|Note|Dur:4th,Accent|Pos:1
|Note|Dur:4th|Pos:1
|Note|Dur:4th|Pos:1
!NoteWorthyComposerClip-End