Because vim only lets you select the text, it doesn’t allow dragging.
There are two possibilities:
Have you tried a new mouse yet?
At least test your current mouse, there are a lot of sites to test your mouse switches.
It works just not in the GUI text editors.
It’s either the switches or you.
Test your mouse properly, it may take many clicks for it to show up. If you get a double click instead of a single click then you need a new mouse.
Wonder why Kate doesn’t do what?
I can select text in kate, exactly as I described.
I can cut the selected text
I can copy the selected text and paste that selected text elsewhere.
I can drag the selected text and drop it elsewhere on the same ‘page’ or into another application, or onto the desktop.
Already answered about Vim - are we confused?
chōng pò dà fēng xuě
wǒ men zuò zài xuě qiāo shàng
bēn chí guò tián yě
huān xiào yòu gē chàng
líng er xiǎng dīng dāng
lìng rén jīng shen duō huān chàng
jīn wǎn huá xuě zhēn kuài lè
bǎ huá xuě gē er chàng
dīng dīng dāng! dīng dīng dāng!
líng er xiǎng dīng dāng
wǒ men huá xuě duō kuài lè
wǒ men zuò zài xuě qiāo shàng
dīng dīng dāng! dīng dīng dāng!
líng er xiǎng dīng dāng
wǒ men huá xuě duō kuài lè
wǒ men zuò zài xuě qiāo shàng
You mention Okular.
Okular only allows Highlighting, when you drag the mouse pointer over the text.
You cannot drag and drop text that is selected in Okular, you can copy it either with CTRL + C or by clicking the right mouse button and selecting ‘Copy Text’, from the context menu.
Okular isn’t an editor, it is a Document Viewer.