The federal labor board’s top lawyers are floating a series of proposals to revamp case processing. The proposals already have worker advocates alarmed about whether the agency will continue to investigate and prosecute allegations of illegal employment actions with the same vigor as the Obama-era board.

National Labor Relations Board General Counsel Peter Robb (R) is considering a long series of changes to board procedures, according to a Jan. 29 “case processing memo” to regional officials obtained by...