thx! I change header size base on gruvbox, now I’m satisfied!
/* .cm-header-4, */
.markdown-preview-section h4
{
font-weight: 500 !important;
font-size: 20px !important;
color: var(--text-title-h4) !important;
}
.cm-header-4
{
font-weight: 500 !important;
font-size: 16px !important;
color: var(--text-title-h4) !important;
}