[Baertram]

It currently should work already with pChat.
But before you right click and choose "copy whole chat" e.g. you need to right click your chat tabs and deactivate all the unwanted chat channels that should not be copied at all of your chat tabs.
It's a bit tricky but a workaround for now.

Example:
You got 3 chat tabs, 1 for chat & zone, 1 for guilds, 1 for group and other.
Right click tab 1 "chat & zone" and choose properties/settings, deactivate all chat channels.
Right click tab 2 "guilds" and properties/settings, deactivate all chat channels.
If you copy all text now via pChat it should only contain the chat from your 3rd tab (group etc.) in the popup window.

Be sure to enable the disabled chat channels afterwards again or you won't see the chat of these channels anymore.


Edit:
Or you just use "Copy discussion". It will JUST copy the channelCode texts of the active chat channel.
Like if you right click a "say" message it should only copy the "say" messages, and if you right click a "zone" message it should only copy the zone messages.

You can also have a look at teh pChat comments, first "sticky" post contains a beta version you could try.
It got reworked in total but adds chat channel filters to the chat copy dialog now.