RE: Edit in Excel - Changes made to read-only fields will be reverted
Hi,
"Changes made to read-only fields will be reverted, Continue?" means there are some fields that are read only. The Editable property is false for those field like EU 3-Party Trade, so you cant modify that.
If you change the value in excel for a read only field, it wont be updated. That's why the warning appears.

In order to add Line No on General Journal Page, you need to create a page extension.
layout
{
addafter("Posting Date")
{
field("Line No."; Rec."Line No.")
{
ApplicationArea = All;
}
}
}