OK, have fun.
Until you learn to download the RSSI data stream as a List or a csv, everything you do might be for naught.
BLE ESP32. Bluetooth. Send. Receive. Arduino IDE might help you. There are several examples shown; use one of the examples to generate a List or a csv.
To create any chart you need two paired values. In your case you need an RSSI value (which appears your Esp32 provides) AND a distance value. You say you cannot use gps values. You expect to generate (calculate) corresponding distance values. The science is a bit uncertain. " Can Bluetooth work out distance? Using bluetooth for localization is a very well known research field (ref.). The short answer is: you can 't. ... Using bluetooth you can at best obtain a distance resolution of few meters," from cocoa touch - How to measure distance between two iphone devices using bluetooth? - Stack Overflow. Similar articles show other ways to derive a distance based on the strength of the bluetooth signal at the receiver. See
https://community.estimote.com/hc/en-us/articles/201636913-What-are-Broadcasting-Power-RSSI-and-other-characteristics-of-a-beacon-s-signal-#:~:text=At%20maximum%20Broadcasting%20Power%20(%2B,Measured%20Power%20(see%20below).
Take you pick of method to capture the received signal level and calculate a distance. Include the 'distance' you calculate in a List of pairs along with your corresponding RSSI. How you include the derived 'distance' in the List of pairs is accomplished exactly the same way one would input a gps derived distance. Your challenge will be to create a List of pairs before you create your graph and actually do the complex distance determinations the above articles allude to.
Create a List of pairs on your Android of the RSSI/distance data.
Someone might be able to help you with Highcharts after you can download the RSSI values and calculate the 'distance'. They need to know how your data List is constructed and someone then might be able to help.