(The new unit sys­tem menu in FreeCAD 0.21dev.)

FreeCAD requires a sin­gle unit sys­tem to be used through­out the entire pro­gram, even if mul­ti­ple files are open. One of the con­se­quences of that design is that cre­ators who work with mul­ti­ple unit sys­tems have to switch back and forth between sys­tems reg­u­lar­ly. Until now this was quite cum­ber­some, buried in the Pref­er­ences dia­log. Thanks to a new menu from devel­op­er @Pad­dle­Stroke, there is now an alter­na­tive. With the merge of PR 8870, FreeCAD now has an always-avail­able menu for quick­ly chang­ing the unit sys­tem in use.