Control the row position in form

When a form is opened from another form, the current position is always set to the first row. With positioning, you can control the row that is preselected when the form is opened. The Position section Source Field property on the relation to the form controls which row will be pre-selected and displayed when the form is opened.

There are several ways that you may want to control the row position when a form is opened. The Source Field must match the target form field in number and type for the positioning to work.
Open to the same record as the parent form record
Set the Source Field property to the primary key of the parent form record. When the form opens, it will open to the same record as the parent form.
Open to a position depending on a field value of the parent record
Set the Source Field to the field of the parent record you want to use. For example, an account form and a country form may have a relation between them that specifies the account.country_id as the positioning Source Field. While in the account form, suppose the user is on a record with a country field value of "USA". If the user then opens the country form from the account form (through a Zoom form, for example), the country_id ("USA") will be preselected in the form instead of the first record. Often this will be a field that corresponds to a foreign key. (For example, the account table has a foreign key to the country table.)