/etc/Muttrc.d/notmuch.rc is in mutt 1.7.2-1+deb9u1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | # --------------------------------------------------------------------------
# FUNCTIONS - shown with an example mapping
# --------------------------------------------------------------------------
# open a different virtual folder
bind index,pager X change-vfolder
# read entire thread of the current message
bind index,pager + entire-thread
# modify (notmuch) tags
bind index,pager \` modify-labels
# generate virtual folder from query
bind index,pager \eX vfolder-from-query
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