Created attachment 188094 [details]
"Open With" side window

SUMMARY
When right-clicking a .pdf file in Dolphin and hovering over the "Open With" option, a side window shows up with alternative apps that can open the PDF. This list however does not include the application "Okular". This leads to some unexpected behavior: when I for instance configure the following "Application Preference Order" in the "File Type Editor" window:
1. Firefox
2. Okular
3. PDF Arranger
...(other apps)
, then right-click a PDF, and hover over the "Open With" entry, then it shows "PDF Arranger" as the first entry in the side window (Firefox isn't shown in that side window, since it is the main app and gets displayed above the "Open With" entry), and displays the text "Middle Click" next to it, which implies that middle-clicking the PDF should open it with "PDF Arranger". However, when I middle-click the PDF, it is opened with Okular.

I only observed this behavior with Okular. Other apps like "Xournal++", "LibreOffice Draw", "Inkscape", "ImageMagick" work as intended: they get displayed in the "Open With" side window and when they are set as the first alternative app (second entry in the "Application Preference Order" list), then middle-clicking the PDF opens it with that app.

Setting Okular to the main app (at the top of the "Application Preference Order" list) works as intended: it is displayed on in the right-click menu above the "Open With" entry, and left-clicking the PDF opens it with Okular.

STEPS TO REPRODUCE
Here I describe how to reproduce the unexpected behavior described above, with the middle-click opening the file with the wrong app.
1. Right-click a PDF file
2. Open "Properties"
3. Press "Change..." next to the "Open With:" entry
4. Place the apps in the "Application Preference Order" field in the following order: Firefox, Okular, PDF Arranger, other apps
5. Right-click a PDF, hover over the "Open With" entry => "Middle Click" stands next to the "PDF Arranger" (see attachment.png)
6. Middle-click the PDF => it is opened with Okular, which is unexpected behavior

OBSERVED RESULT
Right-clicking the PDF opens it with Okular.

EXPECTED RESULT
Right-clicking the PDF should open it with PDF Arranger, if one were to believe the "Open With" side window, since "Middle Click" label is displayed next to this app.

SOFTWARE/OS VERSIONS
(available in the Info Center app, or by running `kinfo` in a terminal window)
Operating System: Kubuntu 25.10
KDE Plasma Version: 6.4.5
KDE Frameworks Version: 6.17.0
Qt Version: 6.9.2
Kernel Version: 6.17.0-8-generic (64-bit)
Graphics Platform: Wayland
Processors: 20 × 13th Gen Intel® Core™ i9-13900H
Memory: 16 GiB of RAM (15.2 GiB usable)
Graphics Processor: Intel® Iris® Xe Graphics


ADDITIONAL INFORMATION