Configuration > Rules > Deduplication to manage merge rules per model. Click on create.

Select the target model (e.g., Contact); once selected, the Domain field becomes available to filter which records are checked, and the Duplicate Removal options for that model can be configured

Select the field that will identify duplicates (e.g., City, Company, Company Name, Complete Name). Each line pairs a chosen field with a Merge If condition (Exact Match shown) to decide when records should be merged.

Merge Action Manager list accessed via Configuration > Merge Action Manager. Use New to create a merge configuration; the list shows each model with Type, Transient Model, and Can Be Merged columns to control which models support merge operations.

Merge Action Manager form to configure a model for merging. Click Enable Merge to activate merging. In Model Description, set the Model technical name and Order (default sort), and optionally enable Transient Model, Has Mail Thread, Has Mail Activity, or Has Mail Blacklist. The Fields tab lists existing fields (e.g., x_name char) and lets you Add a line for new fields; other tabs cover Access Rights, Record Rules, Notes, and Views. Use Create a Menu to generate a menu entry for this model.