I sent a bitcoin transaction without a transaction fee. (ok, I'm learning). It was rejected from the node but it still shows up in coinomi as waiting for confirmation. How do I remove that transaction from coinomi so I can resend it with a transaction fee?
Maybe you need to wait for it to get rejected from itself.
Actually it depends on which api they are using to monitor the network.
Unless that network gets propagated fully, you'll have to wait.
OP isn't active for a long time and I think this project is abandoned.