When editing in the Symbol Table, it is not possible to paste. The Edit menu can be dropped, but the Paste menu item is disabled. Actually, all menus except the Apple and Kicad have disabled items. Nor does the cmd-V key shortcut work.
To confirm, copy some text in any program. Now in Kicad, note that the Edit|Paste menu is enabled. Select T to add a Text symbol and note that you can paste into the dialog that opens. Cancelling that, open the Symbol Table. Now Edit|Paste is disabled.
Application: kicad
Version: (5.0.0-rc2-dev-294-gf317b10), release build
Libraries:
wxWidgets 3.0.4
libcurl/7.54.0 LibreSSL/2.0.20 zlib/1.2.11 nghttp2/1.24.0
Platform: Mac OS X (Darwin 17.4.0 x86_64), 64 bit, Little endian, wxMac
Build Info:
wxWidgets: 3.0.4 (UTF-8,STL containers,compatible with 2.8)
Boost: 1.61.0
Curl: 7.43.0
Compiler: Clang 7.3.0 with C++ ABI 1002
Build settings:
USE_WX_GRAPHICS_CONTEXT=ON
USE_WX_OVERLAY=ON
KICAD_SCRIPTING=ON
KICAD_SCRIPTING_MODULES=ON
KICAD_SCRIPTING_WXPYTHON=ON
KICAD_SCRIPTING_ACTION_MENU=ON
BUILD_GITHUB_PLUGIN=ON
KICAD_USE_OCE=ON
KICAD_SPICE=ON
I'm marking this as "low" simply because this dialog's pretty much unusable on Mac to start with.