HOW TO USE OR IN SEARCH PARAMETER

@serviceac1 can you add more detail. 
A dashboard has no info, you're probably talking about reports. 

Sounds like you have 2 reports, and you'd like to combine the data sets by combining the report filters. 

In general: 

condition A

condition B

condition C

OR:1:condition D

OR:2:condition G

If the OR:1 or OR:2 has multiple parameters try 

OR:1:AND:1:condition D

OR:1:AND:1:condition E

OR:1:AND:1:condition F

OR:2:AND:1:condition G

OR:2:AND:1:condition H

OR:2:AND:1:condition J

Hi ServiceAc1, can you provide a bit more detail?  The dashboard is not an object with an endpoint in the API.  Dashboards are essentially a combination of reports, which in turn are made of lots of different fields.  You can get to most fields via the API.  Are there fields on your reports you're trying to compare?