Showing pending transactions

**Describe the usability problem**

Coming from the BTC community it is quite new to me that I could not send parallel transactions from the same wallet.

**Screenshots**
_If applicable, add screenshots or links to help explain the issue_

**Expected behavior**

I expected that multiple transactions could be sent simultaneously. Alternatively, you could give a warning message in the UI that says you have transactions pending so the user can decide what to do based on what they think the confirmation time for that transaction might be.

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**User impact | Usage frequency | Feasibility scores**

It is just a issue with timing so for me personally it is not so important but it might be to other users.

The issue does not name any files, tests, or entry points. Start by locating the mobile transaction flow and determine how pending transactions are represented in the UI; done would require an agreed behavior for simultaneous sends or a warning that lets users decide how to proceed.

Written by the indexing model from the issue text.