Hi Lachie,
We should know that why there is no merge button in Duplicated Records Detected dialog:
because Merge function is based on two existing records, when we're creating a new record, the Duplication Detection function will fetch our fields data to retrieve whether there was previously existed matching records, however, during this period, the new data is not actually created(no guid for it).
If you open merge dialog URL you will find the truth:
https://org.crm.dynamics.com/_grid/cmds/dlg_merge.aspx?dType=1&iObjType=1&sIds={a9c0764f-3323-e811-a95d-000d3a109d70};{aea19cdd-88df-e311-b8e5-6c3be5a8b200}
Merge function will retrieve existing records with their unique guid (left and right side in sIds parameter), while in new creating process, guid is not generated, so Merge button is not available.
(ObjType=1 is account)
If you would like to integrate such function in form interface, there is a free solution:
http://www.crmconsultants.co.uk/view-and-merge-duplicates-directly-from-the-record-in-dynamics-365/#wpcf7-f3866-p3919-o1
Direct Download Link:
http://www.crmconsultants.co.uk/wp-content/plugins/email-before-download/?dl=c52955e278fd081ddfdc71aa20fa3022
It will retrieve existing record based on duplicated data and display it on embedded web resource when you're creating or editing a record,
but you should still save the duplicated record then Merge function(dialog) can works.
Another point we should notice is that even if the solution can retrieve existing record and display them successfully,
but there is old deprecated open dialog function Xrm.DialogOptions() inside showMergeDialog function in its raz_DisplayDuplicates.js source code,
which not workds in online 9.0, so you should request developer in your team to rewrite this part of snippet(js source code is editable even if its managed solution).
Regards,
Clofly
