Yes. Put your own aliases, environment variables, and functions in ~/.bashrc.user. That file loads every time you open an interactive SSH session, and platform updates never touch it, so your customizations stay put.
Do not edit ~/.bashrc directly. It is a managed file: when your seedbox or storage box updates, our tools compare your ~/.bashrc against the current template and restore the template version. Editing it is itself what makes it differ, so anything you changed there is gone on the next update.
How to add your customizations
Connect to your service over SSH, then create the file and add your settings:
nano ~/.bashrc.user # for example: alias ll='ls -alF' export EDITOR=nano
Apply it to your current session right away with source ~/.bashrc.user; new logins pick it up on their own. These settings load only in interactive shells, so anything a cron job or script needs should be set inside that job or script rather than here.
For the full technical detail including the installer-managed ~/.bashrc.custom hook and how your PATH is built see Shell customization on PMSS on our wiki.
