I´m using Gimp 2.10 for development of my photos. Working on a number of pictures I want to cut out a defined part of 50%. Every time I have to close the chain to get a fixed ratio of w/h. I´ve searched for a configuration file to start with a closed chain-symbol like in the scaling-tool.
My system is a openSUSE tumbleweed- Linux. I´ve checked the configuration-files in my /home an in the /usr/share/gimp-directories but didn´t found a solution.
You can use either the crop tool or the rectangle select and then copy,
paste as new layer, for example… in Tool Options you can constrain
both the crop tool and the rectangle select to 1:1 aspect ratio.