When you create a relationship between tables TeamDesk offers a drop-down to let users choose a record from the master table.
It works well for relatively small number of records, but not convenient for tables with thousands of records.
Now you can use the "Record Picker" (separate window with an ability to search) rather than drop-down list to choose a record.
To allow "Record Picker" you need to edit desired "One-to-Many" relation and enable "Use the Record Picker rather than a drop-down list" option.
When you select the "Browse Choices" item from the drop-down list, TeamDesk will bring up the "Record Picker" to choose a record in master table.