No, for input this does not (yet) work in LibreCAD. You have to set units to inches and for input calculate the value to inches, 43 feet and 9 inches then is 525 inches. In the dimension text it is shown correctly as 43'-9". As a workaround you can write in the command line @43*12+9<0.
There is a pull request adressing the issue and it has recently been marked as merged into the development version 2.2.1 alpha, but it doesn't seem to work:
https://github.com/LibreCAD/LibreCAD/pull/1178