I don't know if this would be possible to run on that Android panel, but on a normal Linux or Windows system you could create a simple NodeJS script (JavaScript) that would spin up its own web server and allow reading of that file via sending HTTP requests from the HMI to your NodeJS web server script that would then send the data back to the HMI user.
Please note that this way you should only implement writing files when all clients that are able to access the system from the network are completely locked down as otherwise potentially everyone with network access to your NodeJS server could write to that file.
However, first of all I would check with Bosch Rexroth if executing arbitrary NodeJS files that runs as servers is actually possible on these devices.
Please note that WebIQ Server does not support Android, only Windows and Linux. So you can use an Android Panel to display the HMI - as long as the browser is supported - but WebIQ Server (Runtime) has to be run on another system.
Websites in general cannot access local data without the user uploading it explicitly.
