I'm not aware of any way to manually drop leagues.

You can try to open a support ticket with DC. That's what I had to do when staking first went live, as I was in a league I didn't have enough SPS for. Here is the support link... https://doublecoconut.freshdesk.com/support/tickets/new

May I ask why you are dropping?

Also I did not know this until just last week but you don't need discord installed to go view the SPL discussions there. Just click on the little discord link. I thought it had to be installed this whole time.

I'll add a request in Discord for a way for players to drop leagues if they wish to.