There was no rest of the output, just that error.
I tried the steps on the Dedoimedo page you linked.
Nothing changed, just the output error of the kbuildsycoca5 command went away after restoring to system menu.
So being a MS system administrator but a Linux layman, I tried a clever approach.
Before the last update round the icon was there, but the kbuildsycoca5 output problem possibly already present.
I update once a month mostly.
I updated on July 14th, and then again on August 17th.
I went back to the VM copy of August 17th, before the update (so the state of July 14th).
The Kdenlive icon was present in the menu, and in the Favorite bar.
I know that would be the case, since it disappeared after the update round of updates that were released between July 14th and August 17th.
First I thought it would be good to get rid of that kbuildsycoca5 error.
I gave the command kbuildsycoca5, just in my session, in Yakuake terminal.
It gave the following error, it is the only error, like before.
kf.service.sycoca: The menu spec file contains a Layout or DefaultLayout tag without the mandatory Merge tag inside. Please fix your file.
Then I did the trick from Dedoimedo:
Right-click Start, Edit applications, in the KDE Menu Editor clicked Edit, choose Restore to system menu and confirmend.
Gave the command kbuildsycoca5 again within my session, the error was gone.
Then in System settings, I changed Icons from Breath to Breath2, since the Breath theme was replaced by Breath2 in a previous update this year but Icons was not changed to Breath2 automatically.
It gave me the new Kdenlive icon from version 20. (I think).
After reboot icon still there.
I logged out and did the trick from Aragorn:
In tty entered the commands:
rm -f ~/.cache/*.kcache
Logged in again, icon there, after reboot icon still there.
Then I installed the 476 updates again like I did five days ago.
After updating the Kdenlive icon was still there.
After the reboot is was gone.
Kdenlive version at July 14th after updating: 20.04.1
Kdenlive version after the updates now: 20.04.3
My guess is that the Kdenlive update is not correct. I don’t know where menu icons come from in linux.
The icon shows up in the KDE Menu Editor, both in the menu at the left as in the appliction details.
When I rightclick Kdenlive in the Plasma menu and choose Pin to task manager or Add to Desktop, it creates a visible icon.
Is it possible that it’s just the incomplete Kdenlive update and that it will be resolved in a next update?