I use Geany in Ubuntu to write C++ code but using IDE standard terminal (pressing F5 to execute code and not opening a new terminal and typing ./a.out).
I can only run one program per time. Is it possible to run 2 or more programs at the same time in Geany?
It's not possible using default F5-execute command. If you want to start multiple instances of your application I recommend to use multiple terminals e.g. with multiterm or some wrapper. For 2nd opportunity you might want to check https://softwarerecs.stackexchange.com/