Is it possible to cast bestow curse twice on the same target using a spell slot of 5th level or higher (so it doesn't require concentration) to bestow different curses? I can't see anything in the spell description that forbids this, but it seems like it could be cheese. I'm especially interested in bestowing the "Wis save or suck" (3rd effect on the spell page) and imposing disadvantage on Wisdom saves and ability checks (first effect on the link above).
According to the PHB on page 205 (SRD link) different spells add together but the same spells do not.
The effects of different spells add together while the durations of those spells overlap. The effects of the same spell cast multiple times don’t combine, however. Instead, the most potent effect—such as the highest bonus—from those castings applies while their durations overlap.
Instead the most powerful version of the spell would from the casting. If they were the same spell slot level used then it would be up to the DM in this case to determine which one is active on a creature.
This assumes the creature fails both saves and what you are going for is for the creature to make disadvantage wisdom saves to be able to take an action.