This is a request for concealing \mathbf similarly to \textbf. Unfortunately, just adding mathbf at https://github.com/lervag/vimtex/blame/master/after/syntax/tex.vim#L31 does not seem to suffice, perhaps due to group nesting?
Thanks in advance.

Minimal working example

Please provide a minimal working LaTeX example, e.g.

\documentclass{minimal}
\begin{document}

\textbf{foo}
$\mathbf{foo}$

\end{document}

Minimal vimrc file

Please provide a minimal vimrc file that reproduces the issue. The following
should often suffice:

set nocompatible

" Load Vimtex
let &rtp  = '~/.vim/plugged/vimtex,' . &rtp
let &rtp .= ',~/.vim/plugged/vimtex/after'

" Load other plugins, if necessary
" let &rtp = '~/path/to/other/plugin,' . &rtp

filetype plugin indent on
syntax enable

" Vimtex options go here
set conceallevel=2
let g:tex_conceal="abdgm"