[question] How do I map Ctrl _ and Ctr +?

[sesm]

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• I know this plugin is about persisting changes to the Vim support built into Obsidian, plus some bonus features, and considered asking in the Obsidian forum first.

Describe the question
I'm trying to do the following mapping in .obsidian.vimrc

exmap foldall obcommand editor:fold-all
exmap unfoldall obcommand editor:unfold-all
nmap <C-_> :foldall
nmap <C-+> :unfoldall

And it doesn't work

However, this works as expected:

exmap foldall obcommand editor:fold-all
exmap unfoldall obcommand editor:unfold-all
nmap <C-o> :foldall
nmap <C-p> :unfoldall

How do I correctly map Ctrl _ and Ctrl + in .obsidian.vimrc?