If you want to be able to use *hax to boot rxtool most of the time but something else (like HBL) on occasion then you will have to do one of two things. Either manually rename the 3dsx files to change what is loaded on exploit execution (tedious and time consuming, plus you can't load HBL from inside emunand) or use a boot manager like ctrbootmanager or bootctr. You would set the boot manager up to be loaded upon *hax execution and then configure the manager to boot specific 3dsx files based on conditions. For ctrbootmanager, you set it to automatically load a default file or open a menu for you to select what to run. Bootctr allows you to configure different 3dsx files to load based on what button you are holding.