[ENHANCE] Custom submit prompt shortcut: few issues

[mydeveloperplanet]

Using Ubuntu 22.04, devoxxgenie 0.4.16

A few issues exist with the custom submit shortcut:

1. The command checkbox is disabled on linux

2. When disabling all checkboxes, the text in the submit prompt shows '+ ENTER to submit prompt...', this should be 'ENTER to submit prompt...'
3. When disabling all checkboxes, it is not possible anymore to create a new line in the prompt.

Concerning 2 and 3: I do not mind that I cannot use ENTER for the submit prompt button, but then it should be prevented to configure this (it should be a radio button instead in that case).
If you do want to allow ENTER for the submit prompt button, shift+enter should be allowed to create a new line in the prompt.