Clarification on app desktop files

I’m trying to include a desktop file for my snap (p4merge in this case), and following the instructions on the build-snaps/metadata note that:

Alternatively, you can create a snap/gui/ directory at the root of your snapcraft project to host a desktop file

I’ve tried the above, with both snap/gui/p4merge.desktop and gui/p4merge.desktop with no luck (by which i mean there is no P4Merge application listed in the launcher). Examining the installed snap itself, i see the p4merge.desktop file:

$find /snap/p4merge/current/ -name '*.desktop'

/snap/p4merge/current/snap/gui/p4merge.desktop

Full snapcraft.yaml:

name: p4merge
version: "18.2"
summary: Helix Visual Merge Tool (p4merge)
description: |
  Helix Visual Merge Tool (P4Merge) is a three-way merging and side-by-side file
  comparison tool. Use it to visualize your merges, obtain comprehensive file
  history, and compare a broad range of image files.
# How to use an icon file provided by a part as the snap icon ?
#icon: lib/P4VResources/icons/p4merge.svg
grade: devel
confinement: devmode


apps:
  p4merge:
    command: desktop-launch $SNAP/bin/p4merge
    # Docs note that you can 'create a snap/gui/ directory at the root of your
    # snapcraft project to host a desktop', but this doesn't seem to work,
    # either as snap/gui/p4merge.desktop nor gui/p4merge.desktop
    #desktop: ./snap/gui/p4merge.desktop

parts:
  p4merge:
    plugin: dump
    source: https://cdist2.perforce.com/perforce/r18.2/bin.linux26x86_64/p4v.tgz
    after: [desktop-qt5]
    stage-packages:
      - libxslt1.1