But would like to also see all unresolved issues in that branch displayed on MR decoration. As it is displayed in overall code section of SonarQube website.
There isn’t a way to do this because it runs counter to the underlying principles. The point of analyzing an MR is to make sure the code you’ve changed/added is clean and to not be bothered by issues in code you didn’t touch. I.e. the point is to Clean as You Code.