Here the 1874 RLDS edition omitted the subordinate conjunction that after the verb know, giving “for I know he granteth unto men according to their desires”. The 1908 RLDS edition restored the original that. Either reading is theoretically possible. For another example where the 1874 RLDS edition omitted the that after the verb know, see under Alma 5:45. Also see the general discussion under that in volume 3.
Summary: Maintain in Alma 29:4 the original subordinate conjunction that after the verb know (“for I know that … ”).