when i use nvim, <C-`> keymapping does not working in tmux

i have been used Ctrl-` and Ctrl-= keymapping for telescope.nvim and work fine. but when i use Ctrl-` and Ctrl-= keymapping in tmux, it does not working and get error

• E20: mark not set vim
• E21: cannot make changes

what is wrong with me? other keymappings work fine in tmux. please help me

environment: mac + iterm2 + zsh

Most terminal apps can only recognize the following ctrl chars:

• Ctrl-A .. Ctrl-Z
• Ctrl-@ Ctrl-[ Ctrl-\ Ctrl-] Ctrl-^ Ctrl-_

and they cannot tell the difference between, for example, Ctrl-i and Tab, Ctrl-M and Enter, Ctr-[ and Esc, ... (more details here).

Nvim uses libtermkey which can recognize more ctrl sequences but for tmux, Ctrl-` is the same as ` so tmux just forwards ` to nvim. And for Ctrl-=, nvim would receive =.

As a workaround you need to use other keybingings which both nvim and tmux can recognize.