RUT955 can already show how RSSI value was changing over time. This graph can be seen from "Status -> Graphs -> Mobile Signal" menu.
We do not have plans to adding more parameters to these graphs in the near future. If this is a necessary functionality for you, you can contact for your Teltonika sales manager for possibility to change router's graphs according to your needs.
Nonetheless, take note, that all these parameter's values (RSSI, RSRP, RSRQ, SINR, etc) could be read from the router either by connecting to router via SSH or by using one of router's monitoring protocols (e.g. SNMP). I.e. You can periodically read desired data from the router and then make a graphical representation of it in your server/computer.