He had joined the Fife club from Falkirk in February 2020 and famously scored the winning goal in the Pyramid Play-off final that defeated Brechin City to secure a place in the Scottish Professional Football League for the first time after winning the Lowland League.
In announcing his six-mile move from New Central Park, his former club said he had “introducing an attractive playing style” and was “popular with the Kelty faithful”.
Former Airdrie United midfielder McDonald, 39, who previously managed Musselburgh Athletic, initially joined Kelty’s coaching staff in 2021.
The arrival of the new management team comes as a company run by England-born, United States-based businessman James Bord is in the process of concluding a buy-out of the current majority owners, German football investment group Fussball GmbH.
Dunfermline had been looking for a new team boss since James McPake was axed after successive defeats left his side second bottom.
Youth boss John McLaughlan has been in caretaker charge for three games – a draw, win and defeat against teams in the top four – but they remain ninth, two points behind Hamilton Academical and having played two more games.
Amid reports of interest in Tidser, who had played 11 times this season, Kelty slipped from second to third place in League 1 and are currently a point behind Stenhousemuir and three adrift of Arbroath.
Kelty’s statement made no mention of a successor but thanked captain Thomas O’Ware and “the backroom team for their exceptional efforts in leading the team over the past couple of weeks” while Tidser was missing from the dugout during negotiations.