Feature request: Append/Replace Mode for each Field

[muart]

Hi Aaron,

This is a super plugin!

I'm running into an issue with the plugin always appending/prepending to the field contents. Some fields, like title, I want to replace the contents and occasionally the contents of a field that normally would be best to append to, like keywords, I want to replace.

Do you think it would be possible to add to the options a toggle for the write mode for each field? So each field could be set to be either replaced or appended?

Thank you!