I connected to a nas in KDE. I wanted to open a folder in nas using vscode, but I couldn’t find the remote location from other locations. I tried the same thing in Gnome and Xfce, and the result was no problem.
Hi and welcome to the forum 
You would need to first mount the remote location in the nas before it is available for the rest of the system.
Those other Window manager’s might have something that can browse remote locations but that’s not something default for a linux system.
No idea if KDE has any extensions/plugins/etc that assist you to browse networked shares, i don’t use those…
Avahi daemon is required for service discovery - an is not default enabled.
systemctl enable --now avahi-daemon
More troubleshooting can be found in [root tip] [How To] Basic Samba Setup and Troubleshooting
You automate/simplify mount using GVFS and gio mount scripting also describe in above guide.