When preparing an answer to the NLNET AppBundler.jl grant application, I collected multiple impressive examples in a Slack thread on the GUI applications made in Julia. Perhaps this list can answer your question:
- Makie: https://makie.org/website/blogposts/showcases/
 - Makie: GitHub - rakeshksr/ImageColorThresholderApp.jl: GUI tool for thresholding color images
 - Makie: https://www.youtube.com/watch?v=tv7-nGiik-w&t=66s
 - ClmGui: https://arxiv.org/pdf/2407.07207
 - QML: GitHub - PeaceFounder/PeaceFounderClient: A voting client for PeaceFounder system.
 - QML: https://www.youtube.com/watch?v=__VP9cLe2HA
 - Gtk: MPIUI.jl/assets/mpilab.png at main · MagneticParticleImaging/MPIUI.jl · GitHub
 - Mousetrap: Mousetrap · Mousetrap
 - Electron: GitHub - JuliaHealth/KomaMRI.jl: Koma is a Pulseq-compatible framework to efficiently simulate Magnetic Resonance Imaging (MRI) acquisitions. The main focus of this package is to simulate general scenarios that could arise in pulse sequence development.
 - Genie: https://genieframework.com
 - SDL2: GitHub - NHDaly/PaddleBattle.jl: Example game written in julia using SDL2