This was introduced a long time ago as a workaround for gathering focus problem -> #131
So the delay has nothing to do with slowness, but is there intentionally.
Now when looking at this I believe the root cause of the focus problem was in the lxqt-globalkeys and its "catching" of shortcut on KeyPress intead of KeyRelease. That was addressed recently (I don't remember the exact time).

Now removing the delay doesn't introduce any focus problems for me. I'll make a PR for others to confirm also.

@jetibest Can you, please, check if #1771 fixes this and doesn't cause any other problems?

@palinek That's unexpectedly fast. This explains a lot, thank you.

I would like to try it, I've already tried cloning the repository and checkout your menu-drop-delay branch, but I'm not sure how to compile this. I'm not very familiar with build tools in general.

The readme says something like: "To build run make, to install make install which accepts variable DESTDIR as usual." However, there is no Makefile. Then I tried running cmake (seeing there is a cmake directory), but that doesn't work out either. Any ideas?

If you don't intend to develop LXQt or use your self-built components in the future, then don't bother with the building feature branches.
As you're on arch, you can wait until PR merged and use the git versions of packages from AUR.

Nevermind, reading the error message more carefully I found out about lxqt-build-tools. I followed the instructions, which is sort of like:

export CMAKE_INSTALL_PREFIX="/usr"
mkdir build
cd build
cmake /opt/lxqt-build-tools
make
sudo make install

And then repeated the same for lxqt-panel. This worked out well. As for the installing, I just copied the necessary files from /usr/local to /usr to apply the newly compiled files, this worked fine too.

After restarting lxqt, I can now see that the delay is gone, but a new problem exists with quickly typing something (again something I'm not used to in KDE Plasma). As far as my initial description of the problem goes, this is sort of the same issue, but I could open a new issue if you want.

If I previously searched using Super_L + "konsole", then wait for the results, and then press Return. It opens Konsole. However, if I then quickly type Super_L + "dolphin" + Return, before any search results show up, then it will again open Konsole (the previously opened one). Expected result is that Dolphin is opened instead of Konsole. This only works if Return is pressed before any result can be returned.

Also, after using: Super_L + "aoeuaoeu" (anything that does not exist) + Return, then after pressing return, the focus is lost. I cannot go back to correct the spelling. In reality, I do see that one of the folders is highlighted in blue just before it collapses to show that no results are found. If I do not press Return quickly, then it does not lose focus. Pressing ESC does return me to giving the start menu, but still, the focus is not in the Search bar.

sudo make install

Installing directly from the source may cause two problems in all distros: (1) You may inadvertently install it under /usr/local, which could cause a headache later; and (2) the package manager won't be aware of the installation.

In Arch and its derivatives, you almost never need to do so. instead, use/make a PKGBUILD and create an installable package.