In Veracrypt, first go to Menu > System > Settings > Edit Boot Loader Configuration
When you press it, it would warn you that inexperient users should never attempt to manually edit boot loader configurations.
Therefore, please make sure you have your important data backed up. Also make sure your Veracrypt Rescue Disk is available, whether it is in a USB or optical CD.
I am not responsible for the damages caused by your own modification to the boot loader configurations.
A pratical suggestion is that, when you misconfigured something, you can always change those settings back and boot normally.
The bootloader configuration file is called DcsProp under \EFI\Veracrypt\ in the EFI System Partition.
Here is a DcsProp file: https://github.com/veracrypt/VeraCrypt-DCS/blob/master/Library/VeraCryptLib/DcsProp
Basically, the comments within that file offers a brief description of each XML tag.
So, a typical modification would be changing the value of to Enter you password: .
If you want to include newlines within your message, simply put a newline in the config file. (Since the XML parser only recognizes angle brackets and the on-exit-parser only recognizes parenthesis)
The "ActionSuccess" or other Actions can be set to Message(msg), where the messages are within the parethenses without quotes.
Note that if some tags are missing from your DcsProp file, their default values would be determined here.
You can enable touch screen mode via the "PasswordType" tag. (but I think you probably won't like it) The result would look similar to this video.
Note that the "PasswordPicture" has to be in the BMP (BITMAPINFOHEADER) format, or it would print a "BmpToBlt - Unsupported" error message.
Finally, this is a glimpse of my own bootloader screen: