Command for joining terminals: workbench.action.terminal.joinInstance
.
Necessary conditions I can think of:
- Terminal tabs are focused.
- Two or more terminals are selected in the terminal tabs.
The best I came up with is:
terminalProcessSupported && terminalTabsFocus && !terminalTabsSingularSelection
But the above is not the same as terminalTabsMultipleSelections
(which doesn't exist).