Setup a submission template:
> echo "--SUBMISSION--" > ~/.commit_template.txt

add it to .gitconfig:
[commit]
template = ~/.commit_template.txt

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0) Commit
1) Default Commit template present in the text area
2) Choose "Amend Last Commit"
3) Dialog ask if previous commit text should be used. (Answer YES)
4) Previous commit text is not replacing the exiting text already present in the text area

NOTE:
1) If there is no text in the text area, this works as expected.
2) This is not in any previous version before the UI change.