To create a custom hyperlink on an object in Omnibar, first we'll have to create that field in Salesforce.
Create a new field formula field that returns text on the Object of your choosing. For this example, we'll use the Contact object, and our objective will be to create a hyperlink button to the Salesforce page containing all related Opportunities of the Account to which a Contact belongs. The new field Label should be whatever you want to see as the Label in the Omnibar view, but Name must be prefixed with Groove_ so something like:
Field Label: Opportunities Field Name: Groove_Opportunities API Name: Groove_Opportunities__c
Enter the formula below:
"https://<yoursalesforcedomainhere>.lightning.force.com/lightning/r/Account/" + AccountId + "/related/Opportunities/view"
Next, edit the Contact groove view to include your newly created field just like you would any other field.
Navigate to Omnibar in gmail, refresh omnibar in the top right corner with the three vertical dots, and search for any given Contact. Scroll down to view the blue button labeled Opportunities, click it, and be happily redirected to the specified Salesforce page.
Why did we do it this way? Why not just use a HYPERLINK function in a formula?
Groove's Omnibar doesn't support the HYPERLINK function in formula. Additionally, it's helpful to note that this particular formula structure will NOT be a hyperlink when displayed on a Salesforce page layout.