What a vibrant community we have. A lot of good suggestions that can help @SaravanaR with navigating the data.
The original question from @SaravanaR was, how can users recognize the existence of a Proforma Invoice by looking at the AR Invoice transaction screen. No mention of GIs, but within the transaction screen itself.
I think adding the field to the Invoices and Memos GI as @BenjaminCrisman suggested is likely the best answer as it makes it easier to find see at a glance those invoices generated from Proformas. Adding joins to the Proforma table to the GI and enabling navigation also makes a lot of sense.
If the the user wants the invoice transaction screen to reflect that the invoice was generated from a proforma as stated by the OP (twice), then adding the field through no-code serves that purpose. It appears though that additional coding will be necessary to bring in the Proforma Invoice number onto the screen along with the checkbox, unless I’m miss reading the available fields listing within the customization packet.