Yes, you can change the leverage on trading page before you open any positions.
After position opening, you can click 'Variation Margin' to decrease the leverage. But leverage increase is not accepted now. MoonXBT allows you to hold 1x-150x leverage. If you are not experienced enough, we advise you to hold low leverage.
For example, the margin is 100USDT when you open the position with 100x leverage. But the market is far more volatile than expected. In order to keep risk under control, you can add another 100USDT margin to decrease the leverage to 50 times.