I am exploring the way to monitor my device with SNMP. What I struggle with, is finding the way to query with MibBrowser Tool the variables with the name rather than full OID. I do receive some data, and this indicates to me that connection is established, but I can't interpret the data I receive.

Let me be more specific about some details. On my agent we use the MIBs that were downloaded from net-snmp project: https://sourceforge.net/projects/net-snmp/files/net-snmp/5.7.3/

In particular SNMPv2-MIB.txt and NET-SNMP-EXTEND-MIB.txt

So I have downloaded these two MIBs to the manager computer and successfully loaded them in MibBrowser tool. I expand the SNMPv2-MIB three until I see the object e.g. sysLocation, I click on it, and to read it I need whether to use function SNMPWALK variable, or add .0 at the end of the ObjectID and use function GET SNMP variable.

With the second MIB situation is more problematic. I expand the NET-SNMP-EXTEND-MIB until I see the object nsExtendOutputFull, I execute function SNMPWALK and what I get is multiple values each with individual index at the end. For example in the output window:

nsExtendOutputFull.3.117.76.51             =     23203

However, in the user manual for my device in the section about using SNMP with Linux OS it is suggested to query these variable as follows:
NET-SNMP-EXTEND-MIB::nsExtendOutputFull.\"TRMSsens1\".

So instead of the index after last dot the name of the variable is used. My colleague that has access to the Linux computer confirmed that this query worked for him.

What am I missing to be able to send similar queries from MibBrowser Tool? I get the error "Invalid OID format"