I think it would be really nice and effective if save actions plugin had a feature that would start compiling right after every save. That would be a 'clangd' like feature and would be very easy for us to track down errors and warnings while writing code.
I think it's bad because it might slow down the performance of Geany. I think what you need is called "Linter" which a feature/function that will lint your codes while typing and it will show the errors in a a panel. You may open another issue to request for linter plugin.