Input/Output Pin
Would it be at all possible to add an option so that subcircuit's pins could behave as both an input, and an output at once. (Like you could if it weren't a subcircuit...) This would be really useful for some circuits, and make them less complex. A use case would be a tri-state register where the data could be read in from the data bus into the register, then send back out on the data bus from a sub circuit.
This request is copied directly from an existing request on the original Logisim development page. https://sourceforge.net/p/circuit/feature-requests/76/
Support for inout pins has been also requested for Logisim-evolution (see issue #253). It supports inout pins now at least on the top level. Supporting it in sub-modules and simulation would be require much effort according to this comment by @kevinawalsh. You can work around it by placing tristate buffers only in the top level and splitting the inout port of a sub-module into separate input, output, and output enable ports.