If I have Teal Mask Ogerpon ex in play, am I allowed to use Ogre's Mask to swap it with a different Teal Mask Ogerpon ex in my discard pile?
Yes, that is allowed.
Source: Twilight Masquerade FAQ; TPCi Rules Team (2024-05-23)

Relevant cards

Note: All applicable cards may not be listed below.
SV6_159
SV6_159