TabPanel.AddPanelAt
From Xojo Documentation
Method
TabPanel.AddPanelAt(index as Integer, name As String)
New in 2020r1
Supported for all project types and targets.
New in 2020r1
Supported for all project types and targets.
Adds a new panel at the specified position using the name as the tab caption. The first panel is numbered zero.
Example
The following code adds a panel as the first tab:
TabPanel1.AddPanelAt(0, "First")