Thanks for taking the time to leave feedback! Would you post a screenshot of the first issue you're talking about?
It might help to use keyboard shortcuts. Here are a few (although there isn't one for un-deleting a block):
To delete a Blockly block in LearnToMod, first click on a block (or group of them) then when they're highlighted and the border turns yellow, hit the "delete" or "backspace" button on your keyboard.
To duplicate blocks, use the Ctrl + C and Ctrl + V commands on your keyboard.
In macs, the "control" key may map to the "command" key.