I just hate it, need to remove Krita, stopped using it after Gimp is Wayland native.

.desktop files are essentially used similar to Windows' registry - you create such a metadata file in a specific location, and it acts as a launcher, autostart setup, and file type assignment (so you can easily assign e.g. PNG files to open with Krita by default).

As the wiki says, you can put multiple MIME types (file type descriptor such as "text/plain" or "application/json" or "image/jpeg" and so on) onto one dotdesktop file, meaning you only need a single launcher to support all file types.

Krita explicitly creates quite a few dotdesktop files, each supporting only a single MIME type.

Downside: littered desktop.

Upside: you can easily pick and choose which file types to open with Krita directly.

Most desktop environments actually handle the [samename]. extension.desktop repetition so you'll only have one Krita launcher entry but it will still collate all MIME type support that is present. Want to exclude e.g. BMP files? Delete the .bmp.desktop file.

XDG Desktop files are a mostly standardized way to integrate individual programs into the desktop. For example, a desktop file in /usr/share/applications or ~/.local/share/applications can add programs to the application launcher, both desktop launcher menus and separate apps like dmenu-run; or they can be used to start applications when the desktop session starts by placing them in ~/.config/autostart.

Desktop files can also set properties related to an application. In this particular case, the MimeType field tells the desktop session what MIME types should be associated with the application. For example, my desktop file for Blender associates the application/x-blender MIME type with it, which causes Blender to show up in the Open with... dialog.

The MimeType field is a semicolon-separated list. One desktop file can define multiple associated MIME types for the same application. Krita instead creates a separate file for each association.

My application menu did get cluttered with multiple krita entries.

Which was a minor annoyance.

I'm not sure about this case because I don't use flatpak that much, but to be honest I hate when I install an Electron based program such Freetube, and even though I installed the BIN binary (arch btw, not happened this on Debian based distros) for some reason my package manager decided to install the whole Electron framework with DE included. I get that it depends on it to work, but I don't need 40 Electron packages to show in my Wofi that I would never use, is so ugly. The same with Qt programs and any single KDE app (but I understand in this case)

I mean, yeah I understand that Freetube depend on Electron to work, but why when installing Steam this is not the case?

You're encouraging mediocre work

Gnome shows like a million of open with Krita entries.

This is nonsense. The documentation is readily available, and it takes arguably less time to provide the code to write a single, proper file than to create 50 desktop entries.

This is just ignorance on whoever wrote that part of Krita.