Mutt mail client package - Sidebar variable not recognised

[Robert]

Hi

Error msg : "Error in /home/rob/.mutt/muttrc, line 30: sidebar_visible: 
unknown variable"
This error is reported belonging to an older version of Mutt, but the 
compiled one in use is modern.  Sidebar has been around for a long time 
10+ yrs.
Note: Cygwin Mutt package being used in MSYS2 with the latest updates.

$ mutt -v  # output edited
Mutt 2.2.16 (2025-11-22)
System: MSYS_NT-10.0-19045 3.6.9-aa532e7b.x86_64 (x86_64)
ncurses: ncurses 6.3.20211021 (compiled with 6.5)
libiconv: 1.18

libidn2: 2.3.4 (compiled with 2.3.8)

hcache backend: GDBM version 1.23. 04/02/2022 (built May 14 2022 10:28:17)

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Thanks Robert.