I made a small tool for exactly this annoyance on Plasma: You want a different icon for one application, but you don’t want to switch your entire icon theme, and you don’t want to dig through .desktop files every time. kAppIcon lets you:

Map a custom image, another app’s icon, or a single glyph from any installed icon theme (WhiteSur, Tela, Breeze, Papirus, etc.) to one launcher Do it completely user-level (no root) Batch-apply the same icon to multiple apps Undo the last change Create/edit icons with a simple pixel editor See all your overrides and reset them cleanly

It’s built specifically with Plasma in mind, but works on other freedesktop desktops too. Repo + install instructions: https://github.com/rayman1972/kappicon Also available on the AUR (kappicon / kappicon-git). Feedback welcome. Bugs can be reported via ‘issues’ in the project.