To Merge vendors on mobile, please follow the below mentioned steps:
Step 1: Go to Parties
Step 2: Go to Vendors >> Click on the vendor
Step 3: Click on more >> Click on Merge
Step 4: Select the Main Vendor >> Click on Merge
Step 5: Type MERGE in the text box >> Click on Merge
Note : In the Vendor Section the Main Vendor will be Shown which you have selected.