In System Settings "Startup and Shutdown" Autostart "application properties" file type application /x-desktop the "Open With" field lists executables for opening desktop entries which are executables in themselves. Opening an executable with an executable is non-sensible to me.

I have spent several hours searching for any help or documentation. See [1] at end for detail. Any additional suggestions on where and what wording would be welcome.

For this procedure I am using KAlarm or DejaDupe (Flatpak) installed apps. However the Application section of the dialogue in question will be the same for Evolution, Getting Things GNOME!, LibreOffice or Notes as well.

To Reproduce

1. Application Launcher [button on left of task bar] > Settings > System Settings > Startup and Shutdown > Autostart > Applications list > [+]
2. Add KAlarm or DejaDupe (Flatpak)
   On KAlarm or DejaDupe entry click [Properties] (button at right; 4 horizontal lines)
   The Dialogue "Properties for kalarm.autostart.desktop" or "Properties for org.gnome.DejaDup" displays.
3. If the [General] tab is not open, click it now.
   The first field will display "kalarm.autostart" or "org.gnome.DejaDup"
4. In the field next to "Open With" note an <application (executable) name> and a [Change] button
5. Click [Change] The "Edit File type application/x-desktop File Type Editor" dialogue displays.
6. Note the following

Filename Patterns section:

- *.desktop  
- *.kdelink  
- *.od  

Description:

desktop entry

Application:

[note: all are executables]
Okular and possibly KWrite will be present if only Distro included apps are installed.
My list starts with Evolution as a default [2]
My present Application section list:

• Evolution
• Kate
• Ancestral Quest 16 [WINE]
• LibreOffice
• Getting Things GNOME
• KWrite
• Okular
• glogg
• gedit

The options are move up, move down, add, edit or remove.

The Problem I see

One can run an executable but running an executable to execute or run another executable is what appears to be the case here.
KWrite can open a *.desktop file to edit it, but not run it.
This list are all executables. *.desktop files to function must be executables. This according to Hiks Gerganov's "Guide to Desktop Entry Files in Linux"[3]

The only app that opens automatically at log-in is Getting Things GNOME but how it is opened at log-in by Evolution [the default setting] which itself has to be opened manually after log-in only adds to the conundrum.

[1] I have spent several hours searching for any help or documentation on this particular field in this particular dialogue, using a variety questions and phrasing. The closest I have gotten in documentation is to how to add applications to the list, but nothing on the Properties dialogue or the file type edit dialogue within it. As far as filing a bug report I have had no luck identifying which launchpad Ubuntu package in which this set of dialogues exist which is now a must beforehand. System-Settings would make sense but searches for Autostart in that package turns up nothing.

[2] Since I did not purposely select Evolution for the file type .desktop in System Settings > Applications > File Associations I do not know how it became at the top of the following list in this Application section of the dialogue.

[3] Guide to Desktop Entry Files in Linux at https://www.baeldung.com/linux/desktop-entry-files where it states "To function correctly, desktop entry files must be executable."