In LXQt, unlike LXDE, you have to drag icons to the quick launch. It's the only way to put them there (realistically). Why? I do not know. You can't click on Quick Launch settings in the panel configuration. You have to drag and drop them.
Then, for reasons known only to the developers, you can't drag/drop to sort them. Why? Again, I have no idea. Where you drop them (and it's tricky to just drop them) is a finicky beast and dropping them in any specific order is darned near impossible.
So, I dug into it. You can sort them - and it's relatively easy, if you don't mind getting your hands a little dirty.
Basically, you find the config file and edit it manually by changing the numerical values of the entries.
Why? I have no idea...
(I'm going to miss LXDE for a long, long time.)
Then, for reasons known only to the developers, you can't drag/drop to sort them. Why? Again, I have no idea. Where you drop them (and it's tricky to just drop them) is a finicky beast and dropping them in any specific order is darned near impossible.
So, I dug into it. You can sort them - and it's relatively easy, if you don't mind getting your hands a little dirty.
Change the sort-order in Lubuntu Quick Launch
Lubuntu has gone from LXDE to LXQt. In LXQt there's no way to drag the icons in the quick launch to sort them to your liking. Fear not, you can still sort them. This one is actually pretty easy,
linuxtips.gq
Basically, you find the config file and edit it manually by changing the numerical values of the entries.
Why? I have no idea...
(I'm going to miss LXDE for a long, long time.)