Select the text with the leftt mouse button and press once on the right mouse button to copy on the Windows clipboard.
Now you can paste the copied text in WSL with another right button click, or paste in Windows with CTRL-V.
So when you want to copy/paste in WSL, you select the text and press the buttons left, right, right.
The Preference is somewhere else in Ubuntu 18.04 LTS
In Ubuntu 18.04, the preference menu item is hidden in the top panel:
Once in preference, go to the Editor tab, and change the tab width.
The Spellcheck language is under the Tools menu which is under the ≡ menu button.
Foreign Language input
If you need to add a different ...
I think maybe you can just try using ssh or sftp protocol to transfer the file. An easy way to do it sftp username@ipaddress. When i face such issues where i cannot copy from one sys to another. It comes in handy a lot.
I just tried it on 19.10 and it works for me with gedit 3.34.0 and https://github.com/nymanjens/gedit-intelligent-text-completion/releases/download/v2.4/intelligent-text-completion-gedit3-8-v2.5.tar.gz.
The key point maybe is that you first need to install gedit-plugins from the 19.10 repositories with sudo apt install gedit-plugins.
After doing so, ...