Running Ubuntu 22.04 with ubuntu-mate-desktop added.
When you right-click on a file to open it with gedit,
you want the file to be opened in the current workspace.
Instead the file is opened in the most recently instance of gedit
which is typically in another workspace.
You have to find the workspace where the file is opened and then
separate it to a new window which is moved to the correct workspace.
There are settings in "/usr/share/applications/org.gnome.gedit.desktop"
You can add "-s" to open it in the current workspace, but then you
always open a new window. I.E: One window per file which is undesirable
gedit should always open in the current workspace.
It that means opening a new instance, so be it.
You should be able to have tabbed gedit.