The "Up sensors" map object's file name is tableA2.htm, usually located in C:\Program Files (x86)\PRTG Network Monitor\webroot\mapobjects
Please save it under a new file name and open it in a text editor.
Please change the first line, for example from
<!--Data Tables: UP Sensors-->
<!--Data Tables: UP Sensors Custom-->
In the htm file, you find a block of properties, which ends like this:
Below filter_status="3", please add this line
This expands the table to 100 entries. Other values are of course possible as well. To show all sensors, use count=* but please be advised that this can have a serious effect on the performance and is not officially supported.