Description of the desired feature

Hello dear PyGMT community,

I would like to request a feature that will allow to set a colorbar's length to any desired percentage relative to a map side. Currently, it is set to 80 % by default, and a user needs to provide a specific value with +w modifier to change the colorbar's length. It would be very nice though if one could set any arbitrary number in percents of a map side, like 100 % as sometimes is asked by reviewers during the publication process.

This request is the follow-up to the discussion in the GMT community forums.

Thank you.

Are you willing to help implement and maintain this feature? No, I don't think I have enough skills so far