One way to make the startup faster is to delete plugins that you don't need. Many people load a ton of plugins (including several contrib plugins) that they never use, either because they don't care or don't know, or "just in case". This obviously causes a lot of additional I/O.
I really mean "delete", not "disable", since "disable" will initially still load the DLL, it will just not initialise the plugin. Thus, disabling a plugin still has the same I/O payload at startup.
You can also delete a few lexers if you are 100% sure that you do not use them, although this will not save you a significant amount of time now, since lexer loading has been greatly optimised already. You will only save a couple of dozen milliseconds that way, but still... if you know for sure you will never edit Hitachi assembler or GLSL files, there is no point loading the lexers for that.
Another way to make startup a little faster is to disable "check associations at startup", this option checks a good dozen registry keys each time at startup.
Lastly, you can disable internationalisation if you don't use it, it only saves a few cycles at startup, but everything helps. Same goes for disabling the startup screen.
If you compile Code::Blocks yourself and want optimum performance, apart from using proper optimisation settings, be sure to replace the cbDEBUG define with NDEBUG, this will cut out quite a few kilobytes of code.