ibuffer-always-show-predicates

ibuffer-always-show-predicates is a variable defined in `ibuf-ext.el'.
Its value is

nil

• This variable may be risky if used as a file-local variable.

Documentation:
A list of predicates (a regexp or function) for buffers to always display.
If a regexp, then it will be matched against the buffer's name.
If a function, it will be called with the buffer as an argument, and
should return non-nil if this buffer should be shown.
Note that buffers matching one of these predicates will be shown
regardless of any active filters in this buffer.

You can customize this variable.