From the images that you sent; you mean you make extension of Sales Table and added new fields. If you see now your Datasource has the new fields? so what is your problem?
If you are talking about, make your new custom table extends Sales Table, then you should create new table add the new fields (Company and Mobile number) and set the property Extends in your new table to SalesTable.
Thanks,
Waed Ayyad
If this helped, please mark it as "Verified" for others facing the same issue
I have replicated the same scenario with adding two fields in the existing table and added the table in custom form it was working fine. don't try to drag and drop your table in the form DataSource instead create a new data source and add the existing table in the property level for your reference I'm attaching the images below. If you face any issue, try to put full synchronization.
You're asking in D365 general forum, but your question clearly is about a particular product and not about D365 in general (regardless of the product). Isn't it F&O?
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