Analysis of a LALR shift-reduce conflict
This conflict arises because when the parser is at the beginning of a line and the lookahead is VAR, it can't tell whether or not to reduce an empty maybe_specifier. In this simple grammar, that decision could be resolved with one more lookahead token, making the grammar LR(2), but that might not be true in the original unsimplified version.

So the conflict is not an artefact of the LALR algorithm, and it is important to fix. (The yacc default resolution "choise shift over reduce" will make it impossible to parse lists which don't start with a SPECIFIER.)

A simple fix is to defer the parsing decision for the first entry in a list:

list:
  VAR
| SPECIFIER VAR
| list maybe_specifier VAR
;


Again, that might or might not be useful in the context of your full grammar.