Trainers » Koga's Trap | Attacks » Severe Poison
If I had used Muk & Alolan Muk GX's "Severe Poison" attack that places extra Poison damage counters and in the next turn use Koga's Trap, do they still place the extra Poison damage?
No, they don't. The new, normal Poison Special Condition replaces the old Severe Poison Special Condition.
Source: Unbroken Bonds FAQ (2019-04-19), TPCi Rules Team (2019-05-02)
Attacks » Severe Poison
If I Switch my Active Pokemon that is affected by Poison from Muk & Alolan Muk GX's "Severe Poison" attack and Dust Island is in play, does my new Active Pokemon take the extra damage counters?
Yes, it does. Dust Island specifies that it is affected by "that Special Condition".
Source: Unbroken Bonds FAQ (2019-04-19), TPCi Rules Team (2019-05-02)