Communication with external application

Instead of using the LEDs and Buttons of SimulIDE, I want to use my own "virtual breadboard". Thus I only need the simulation of the Arduino itself. My existing application is programmed in C# and is running on the same machine. Is it possible to send the pin signals from my application to SimulIDE to be processed by the virtual Arduino and then send the outputs of the Arduino back to my application?

The website states that SimulIDE uses simavr under the hood for the actual simulation. Is that true for Windows and Linux? To summarize I need to simulate an Arduino and let it send and receive the pin states to and from my own application (similar to a virtual breadboard with sensors and motors).

Is it possible to send the pin signals from my application to SimulIDE to be processed by the virtual Arduino and then send the outputs of the Arduino back to my application?

You can use serial port connection to connect with another applications or real hardware.
Some info at the end of this page: https://www.simulide.com/p/blog-page_4.html
In this video you can see it working (from 00:45): https://www.youtube.com/watch?v=WVBgmah6gE0
That info is a bit outdated, but you can get the idea.

This topic could also help: https://simulide.forumotion.com/t13-connection-of-multiple-simulide-applications-in-win10

The website states that SimulIDE uses simavr under the hood for the actual simulation. Is that true for Windows and Linux?

Yes, simavr is built in simulide (a modified version).