Hello Nizami_Nz, thank you for your kind words!
I wouldn’t recommend RDT for sensitive data, or even Google Sheets for that matter, because as you said, it’s all legible plain text. Google doesn’t do any server-side encryption, just account auth. When RDT requests the sheet, Google only responds with plain text.
To do this securely you would either A) have a server instance to which the end user sends the user/pass and have the server check the response against the sheet or B) make sure all data is encrypted before even sending it to Google. Then decrypt when you pull from Google.
Encryption is outside of the scope of the plugin, really. There are myriad solutions for this on the marketplace as is, though! For example, this plugin uses TEA and is available for free: DH Key Exchange and TEA Encryption | Fab