To do this glitch, you need to obtain the Makers Sigh potion and lots of it. Start by assigning your available abilities to your tactics menu. Once this is done, use the Makers Sigh potion. Using this potion will remove all your abilities. Now save and reload that save. Go into your ability menu and you will notice that the abilities you assigned to your tactics are already unlocked, but you still have all your unassigned ability points. You can either use the Makers Sigh potion again and save then reload, or assign your points to other abilities, put them in your tactics menu, and repeat the rest of the glitch for even more ability points. This glitch also allows you to unlock certain abilities in classes without having to go through the entire skill tree.