I want to be able to open a (local) terminal over a "mounted" remote folder open with fish protocol.

My usecase: i am developing an application on a test server.
My git private key are on my machine, and i don't want them to leave it.
I mount the test folder with the code on my local machine simpli opening it with "fish://user@server:port/location", modify my files, then I notice the git plugin is not working, so i do "open a console here" but the console localtion is my home folder, not the mouted folder.

I understand that is a temporary mount in a temporary folder, but i can't even find any documentation on where is located. Now i can usse sshfs and actally mount from command line, but that is a real bummer because with fish protocol + git plugin i could do all from the GUI and impress all the ladys.

well, the fish protocol is specific to KIO which doesn't actually mount the remote systems, only provides a unified interface to them for KIO-enabled applications (KDE apps) (at present anyway, there is a proposal out to change it).
This means there is no path for the terminal to start from, so uses a "safe" default of your home directory.

The alternative to KIO is GVFS (used by Gnome apps) which does provide mount points via fusefs, so that you can use it with non GVFS apps like the terminal.

Hello @airdrik can you please explain what is required to use gvfs on kde (kubuntu)

I don't have details handily available, having generally avoided gnome apps. What I know about gvfs providing actual mount points came from some recent discussion about adding that functionality to KIO, notably viewtopic.php?f=83&t=141917

I'd guess the way you'd accomplish it is use a gvfs-based file manager (nautilus, nemo, others?) to set up the connections to the remote server. Then you should be able to browse to the provided mount points in either dolphin or the terminal and issue your git commands.