How can I open the result of ctrl+] in a new split?
This will do it:
CTRL-W ] *CTRL-W_]* *CTRL-W_CTRL-]* CTRL-W CTRL-] Split current window in two. Use identifier under cursor as a tag and jump to it in the new upper window. In Visual mode uses the Visually selected text as a tag. Make new window N high.
courtesy: D. Ben Knoble