This is how to add an "Open terminal here" entry to the eOS file manager.
Create /usr/share/contractors/openinterminal.contract
with these contents:
[Contractor Entry]
Name=Open terminal here
Icon=terminal
Description=Open terminal here
MimeType=inode;application/x-sh;application/x-executable;
Exec=io.elementary.terminal -w %U
Gettext-Domain=io.elementary.terminal
Restart the terminal, and voilla!