With IfcOpenShell, it is possible to take an input IFC file, and choose between new data to that existing file, which can be saved as a new file, or creating a fresh IFC file with nothing but the new data.
Unfortunately, almost all applications that support IFC do not treat it with priority as a native format. This means that even if you create this new IFC file, and that someone is able to import that file into their BIM authoring tool, the chances are close to zero that they can merge those changes back into their proprietary native format. This means that the next time they export an IFC, the data will be lost again. To change this fundamental behaviour either requires vendors to step up, or for buildingSMART to enforce this style of IFC consumption in the certification process.
Depending on exactly what data your store, it is possible to mitigate this cultural data loss and develop a workflow to bring in your data into their proprietary native format. That is where I mention things like Speckle. But even simpler solutions like providing them with a crafted CSV (most BIM tools have some form of spreadsheed data import ability) or mini plugin for their app may be possible.