feature request: Choose between Plain text and HTML signaute in composer

Please correct me if this is already possible – I couldn't figure out how.

I have several signatures, all of them have a HTML Variant defined.

What I would like to do is to be able to only use the plaintext / markdown variant if I choose to only send a plaintext message (and /or use no HTML) or if I'm replying to a plaintext-email.
When sending a new message, the choice should / could be derived either from history or on whether HTML would be generated anyways.

Basically my problem is: How to tell the composer to use the plaintext variant of a signature?
The composer alswys creates HTML and I would prefer to not have to create two versions of every signature.

Thanks!