Often times, when applications get slow, its because they're leaking memory, which is not a problem you're going to be able to solve without access to the programmer's code.
You can give yourself more time with the application by freeing up as much working memory on your Mac as possible -- quite all apps you don't actively need. Close browser windows, etc.
Open "Activity Monitor" to see a list of what's running on your Mac. Double-click on the app's name, then take two samples, not too far apart in time. Compare the resulting two files with "diff" (if your editor doesn't have this feature, the Mac's terminal does). You may find an interesting lead there.
More simply, and more generally with commercial software, consult their support website or forum for similar problems &/or solutions from other users. Consider filing a bug, with as precise information as you can collect.