Hai Velera,

To change picture in composer from thumbnail to medium you can update from front site or backend, you go to post->click picture you want to change-> image source-> choose medium->done editing and update post

see my video tutorial- http://screencast.com/t/EWfBVbhE

Hope this help.

I understand it. I want the default: Medium.

Hello Valera,

I'm sorry but there is no setting to change the default to medium.

I understood. Thank you.

Hello Valera,

You're welcome.