[watergatorman]

Answering my own question, Geany has "Sending text through custom commands" and ability to add custom commands via "Send Selection to->Set Custom Commands"

But it looks like this just replaces the selected text so it may be more for formatting.

I prefer a new window to open so the selected text isn't altered.

I know I can program vEdit+ to do this, but that is not Linux.

[watergatorman]

You need to look at TUIs (Text User Interfaces).